.......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2 Ba kho chứa 240 tấn thóc .Nếu chuyển 25 tấn từ kho thứ nhất sang kho thứ 2 Sau đó chuyển 35 tấn từ kho thứ 2 sang kho thứ 3 thì số thóc ở 3 kho bằng nhau .Tính số thóc mỗi kho. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3: Ba lớp 4a;4b;4c. đi trồng cây cả 3 lớp trồng được 120 .Số cây lớp 4a và 4 b trồng được là 70 cây ;số cây lớp 4b và 4c là 90 cây ;số cây lớp 4c và 4a là 80 cây . Tính số cây mỗi lớp . (Tham khảo thêm Đề thi và phần Bài tập mở rộng) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 13.DẠNG TOÁN KHỬ Bài 1: Mua 3 lọ mực và 4 cái bút hết 25000 đồng . Mua 5 lọ mực và 4 cái bút hết 31000 đồng . Tính giá tiền mỗi loại. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 50
.......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2: Minh mua 5 quyển vở và 8 quyển sách hết 75500 đồng. Tâm mua 3 quyển sách và 10 quyển vở hết 73000 đồng. Tính giá tiền mỗi loại. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3: Mua 3 m vải hoa và 7 m vải xanh hết 370 000 đồng . Mua 4 m vải hoa và 5 m vai xanh phải trả 320 000 Đồng. Tính giá tiền 1m vải mỗi loại. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 4: Minh mua 5 quyển vở và 8 quyển sách hết 42000 đồng. Biết một quyển sách có giá gấp 2 lần 1 quyển vở. Tính giá tiền mỗi loại .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... *Bài tập 1: Để học thủ công, tổ Một mua 10 cái kéo và 5 túi giấy màu hết tất cả 50.000 đồng. Tổ Hai cũng mua 8 cái kéo và 10 túi giấy màu như thế hết tất cả 52.000 đồng. Tính giá tiền một cái kéo, giá tiền một túi giấy màu? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... *Bài tập 2: Văn phòng trường em lần đầu mua 24 cây bút bic và 12 cây bút chì hết tất cả 60.000 đồng. Lần sau mua 10 cây bút bic và 8 cây bút chì hết tất cả 28.000 đồng. Hãy tính giá tiền mỗi cây bút từng loại? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... *Bài tập 3: Cô Thu mua 1 mét lụa và 1 mét vải hết tất cả 50.000 đồng. Cô Đông mua 1 mét lụa 2 và 2 mét vải cùng loại như thế hết tất cả 23.000 đồng. Hỏi cô Xuân mua 8 mét lụa và 15 mét vải cùng 5 loại như thế phải trả bao nhiêu tiền? .......................................................................................................................................................................... .......................................................................................................................................................................... 51
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 4. Bài tập về nhà: Bạn Mai mua 3 lọ mực đỏ và 2 lọ mực xanh giá 23.000 đồng. Bạn Lan cũng mua 2 lọ mực đỏ và 3 lọ mực xanh mực như thế hết 22.000 đồng. Tính giá tiền một lọ mực mỗi loại? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 14. MỘT SỐ BÀI TOÁN VỀ TÍNH TUỔI Bài 1: Năm nay con 4 tuổi và kém cha 35 tuổi. Hỏi sau bao nhiêu năm nữa thì 2 lần tuổi cha bằng 7 lần tuổi con ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 52
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2: Cách đây 3 năm, em lên 5 tuổi và kém anh 8 tuổi. Hỏi cách đây mấy năm thì tuổi anh gấp 3 lần tuổi em ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3: Tuổi cha năm nay gấp 4 lần tuổi con và tổng số tuổi của 2 cha con cộng lại là 50 tuổi. Hãy tính tuổi của 2 cha con khi tuổi cha gấp 4 lần tuổi con. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 4: Hùng hơn Cường 6 tuổi, biết rằng 4 tuổi của Hùng bằng 2 tuổi của Cường. Tính tuổi của mỗi 73 người. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 5: Năm nay tuổi mẹ gấp 3 lần tuổi con. 8 năm trước tuổi mẹ gấp 7 lần tuổi con.Tìm tuổi mỗi người hiện nay. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 6: Tuổi của bà, của mẹ và của Mai năm nay cộng được 100 năm.Bạn hãy tính tuổi của mỗi người, biết rằng, tuổi của Mai có bao nhiêu ngày thì tuổi của mẹ có bấy nhiêu tuần và tuổi của Mai có bao nhiêu tháng thì tuổi của bà có bấy nhiêu năm. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 7: Tuổi em năm nay nhiều hơn hiệu số tuổi của 2 chị em là 15. Tổng số tuổi của 2 chị em cùng nhỏ hơn 2 lần tuổi của chị là 3. Tính tuổi mỗi người. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 53
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 8: 8 năm về trước tổng số tuổi của ba cha con cộng lại là 48. 8 năm sau cha hơn con lớn 26 tuổi và hơn con nhỏ 34 tuổi. Tính tuổi của mỗi người hiện nay. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 9: Hai năm trước đây tuổi hai chú cháu cộng lại bằng 24. Hỏi sau mấy năm nữa thì tuổi chú gấp 4 lần tuổi cháu? Biết rằng 2 năm trước tuổi cháu có bao nhiêu ngày thì tuổi chú có bấy nhiêu tuần . .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 10: Tuổi em hiện nay gấp 2 lần tuổi em khi anh bằng tuổi em hiện nay.Khi tuổi em bằng tuổi anh hiện nay thì 2 lần tuổi em lớn hơn tuổi anh lúc đó 15 tuổi. Tính tuổi hiện nay của mỗi người. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 11: Khi tuổi chị bằng tuổi em hiện nay thì tuổi chị lớn hơn 3 lần tuổi em là 3 tuổi. đến khi chị 34 tuổi thì tuổi em bằng tuổi chị hiện nay.Tìm tuổi của 2 chị em hiện nay. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 12: Tuổi bố năm nay gấp 2,3 lần tuổi con. 25 năm về trước, tuổi bố gấp 8,3 lần tuổi con. Hỏi khi tuổi bố gấp 3 lần tuổi con thì con bao nhiêu tuổi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 13: Hai người bạn gặp nhau. Một người hỏi bạn mình :\" Các con của anh bao nhiêu tuổi?\" Người thứ hai trả lời: \"Tôi có hai đứa con trai : tuổi tôi gấp 4 lần tuổi đứa thứ nhất và gấp 7lần đứa thứ hai\". Hỏi ông bố bao nhiêu tuổi và các con của ông bao nhiêu tuổi? 54
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Bài 14: Ba người có tên là A, B, C cùng ở trong 1 buồng của toa xe lửa. Trong khi trò chuyện mới biết rằng: - Nếu đổi chỗ các chữ số trong tuổi của A thì được tuổi của B - Hiệu của tuổi giữa A và B gấp đôi số tuổi của C - Tuổi của B gấp 10 lần tuổi của C Hỏi mỗi người bao nhiêu tuổi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 15 : Người ta hỏi một ông già rằng ông đã tham gia quân đội trong bao lâu, ông trả lời:Số năm tham gia quân đội của tôi bằng 1/27 tuổi của tôi hay bằng 1/7 tuổi của cháu tôi hoặc bằng đúng tuổi của con trai tôi. Ngoài ra tuổi của tôi gần số 90 hơn là gần số 100. Hỏi ông già đã tham gia quân đội trong bao lâu? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 16 : An hỏi Hà: “ Năm nay anh bao nhiêu tuổi? ” Anh Hà trả lời: “ Nếu sang năm lấy tuổi của anh nhân với 6 sẽ được một số có 3 chữ số trong đó chữ số hàng trăm là 1, còn chữ số hàng chục và chữ số hàng đơn vị chính là chữ số hàng hàng chục và chữ số hàng đơn vị của tuổi anh khi đó”. Hỏi anh Hà năm nay bao nhiêu tuổi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 17: Vào năm mới tuổi bố nhiều hơn tuổi anh là 29, tuổi mẹ nhiều hơn tuổi em là 25, hiệu của tuổi bố và tuổi mẹ gấp đôi hiệu của tuổi anh và tuổi em. Tính tuổi của mỗi người (bố, mẹ, anh và em) biết rằng tổng số tuổi của bốn người là 90. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 18: Ngày đầu năm 1991, bác Nam hỏi anh Việt: - Năm nay cháu bao nhiêu tuổi? - Tuổi cháu năm nay đúng bằng tổng các chữ số của năm sinh - anh Việt trả lời. 55
Thế mà bác Nam tính ra ngay tuổi của anh Việt. Bác gật gù nói: - Lúc bác bằng tuổi cháu hiện nay, bác đang tham gia kháng chiến chống Pháp, và năm ấy cũng có tổng các chữ số bằng tuổi cháu. Anh Việt cũng tính đúng tuổi của bác Nam. Hỏi anh Việt và bác Nam sinh năm nào? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 19: Trả lời về tuổi của mình, 1 người đàn ông nói như sau: \"Cứ vào sinh nhật của tôi, cha tôi lại giết 1 con cừu để ăn mừng, bộ da cừu ông xếp vào 1 chỗ. Tôi lớn lên lấy vợ cũng sinh được 1 thằng con trai, vào sinh nhật nào của nó tôi cũng lại giết cừu, cất bộ da vào 1 chỗ. Năm nay số da cừu của tôi bằng số da cừu của nó. Hỏi tuổi người đàn ông và con trai của ông ta là bao nhiêu? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 20: Trong giờ nghỉ ở một hội nghị, các đồng nghiệp hỏi một giáo sư xem ông ta có mấy con và chúng bao nhiêu tuổi. Giáo sư trả lời: - Tôi có 3 con trai. Có sự trùng hợp lý thú là ngày sinh của chúng đều là ngày hôm nay, tuổi chúng cộng lại bằng ngày hôm nay và đem nhân với nhau thì tích là 36. Một đồng nghiệp nói: - Chỉ như vậy thì chưa xác định được tuổi của bọn trẻ. - Ồ, đúng vây. Tôi quên không nói thêm rằng: Khi chúng tôi chờ sinh đứa thứ 3 thì 2 đứa lớn đã được gửi về quê với ông bà. - Xin cám ơn ngài, giờ thì tôi đã biết tuổi của bọn trẻ rồi. Vậy tuổi của mỗi cậu con trai là bao nhiêu và ngày hôm đó là ngày nào trong tháng? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 1 Hiện nay tuổi em bằng 2/3 tuổi anh .Đến khi tuổi em bằng tuổi anh hiện nay thì tổng số tuổi của hai anh em là 49 tuổi . tính tuổi hiện nay của mỗi người. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2 Hiện nay bố gấp 6 lần tuổi con . 4 năm nữa bố gấp 4 lần tuổi con .Tính tuổi hiên nay của mỗi người. 56
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Bài 3 Tổng số tuổi của ông ,bố và cháu là 120 tuổi .Tính tuổi mỗi người biết tuổi ông là bao nhiêu năm thì cháu bấy nhiêu tháng và cháu bao nhiêu ngày thì bố bấy nhiêu tuần .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 4 Hiện nay tuổi mẹ gấp 4 lần tuỏi con . Năm năm nữa tuổi mẹ gấp 3 lần tuổi con .Tính tuổi hiện nay của mỗi người. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 5: Tuổi của con hiện nay bằng 1/2 hiệu tuổi của bố và tuổi con. Bốn năm trước, tuổi con bằng 1/3 hiệu tuổi của bố và tuổi con. Hỏi khi tuổi con bằng 1/4 hiệu tuổi của bố và tuổi của con thì tuổi của mỗi người là bao nhiêu ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 57
15. BÀI TOÁN GIẢ THIẾT TẠM VÝ dô 2: 12 con võa gµ võa thá, c¶ th¶y ®Õm ®-îc 32 ch©n. Hái cã bao nhiªu con gµ, bao nhiªu con thá. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... VÝ dô: Cã 18 « t« gåm 3 lo¹i: Lo¹i 4 b¸nh chë ®-îc 5 tÊn, lo¹i 6 b¸nh chë ®-îc 6 tÊn vµ lo¹i 8 b¸nh chë ®-îc 6 tÊn. 18 xe ®ã chë ®-îc tÊt c¶ 101 tÊn hµng, vµ cã tÊt c¶ 106 b¸nh xe. Hái mçi lo¹i cã bao nhiªu xe? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi to¸n 1: Cã 10 xe chë g¹o gåm hai lo¹i. Lo¹i 1 xe chë ®-îc 43 t¹ vµ lo¹i 1 xe chë ®-îc 32 t¹. TÊt c¶ ®· chë ®-îc 39 tÊn 8 t¹ g¹o. Hái cã bao nhiªu xe mçi lo¹i? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi to¸n 2: Cã 8 sät ®ùng tÊt c¶ 1120 qu¶ võa cam võa quýt. Mçi sät cam ®ùng ®-îc 75 qu¶, mçi sät quýt ®ùng ®-îc 179 qu¶. Hái mçi lo¹i cã bao nhiªu qu¶? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi to¸n 3: Mét bÕp ¨n mua 200 con võa Õch võa cua bÓ. Tæng sè ch©n ®Õm ®-îc lµ 1400 ch©n (cµng cua xem nh- ch©n cua). Hái cã bao nhiªu con mçi lo¹i. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 58
Bµi to¸n 4: Cã 15 « t« gåm 3 lo¹i: Lo¹i 4 b¸nh chë ®-îc 5 tÊn, lo¹i 6 b¸nh chë ®-îc 10 tÊn vµ lo¹i 6 b¸nh chë ®-îc 8 tÊn. 15 xe ®ã chë ®-îc tÊt c¶ 121 tÊn hµng, vµ cã tÊt c¶ 84 b¸nh xe. Hái mçi lo¹i cã bao nhiªu xe. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi to¸n 5: Cã 15 « t« gåm 3 lo¹i, lo¹i 4 b¸nh chë 5 tÊn, lo¹i 4 b¸nh chë 6 tÊn, lo¹i 6 b¸nh chë 8 tÊn. Hái sè xe mçi lo¹i lµ bao nhiªu, biÕt tæng sè b¸nh xe lµ 70 b¸nh, tæng sè hµng chë ®-îc lµ 93 tÊn. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 16. CÁC BÀI TOÁN LIÊN QUAN TRỒNG CÂY 59
17. MỘT SỐ BÀI TOÁN GIẢI NGƯỢC TỪ CUỐI Bài 1: Lan có một số nhãn vở .Lan tặng Mai 1/2 số nhãn vở và 1chiếc .Lan tặng Hoà 1/2 số nhãn vở còn lại và 2 chiếc .Lan tặng Nga 1/2 số nhãn vở còn lại sau 2 lần và 3 chiếc .Cuối cùng Lan còn lại 6 chíêc cho Mình .Hỏi Lan có tất cả bao nhiêu nhãn vở ,và tặng mỗi bạn bao nhiêu nhãn vở. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2, Một bà đem trứng đi chợ bán .Lần đầu bà bán 1/2 số trứng và 1/2 quả trứng .Lần 2 bà bán 1/2 số trứng còn lại và 1/2 quả trứng .Lần thứ 3 bà bán 1/2 Số trứng còn lại sau 2 lần đầu và 1/2 quả trứng nữa thì vừa hết . Hỏi bà đem ra chợ bán bao nhiêu quả trứng. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3: Mai có một số bông hồng ,Mai tặng Nga 1/2 số hoa Mai có .Tặng Đào 1/2 số còn lại .Cuối cùng Mai còn 7 Bông dành cho mình .Hỏi Mai đã tặng mỗi bạn bao nhiêu bông hoa. (Tham khảo thêm Đề thi và phần Bài tập mở rộng) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 1. T×m mét sè biÕt r»ng, sè ®ã trõ 80, ®-îc bao nhiªu nh©n víi 5 råi céng víi 192 th× b»ng 792. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 2. MÑ cho hai anh em mét sè tiÒn ®Ó mua s¸ch. NÕu anh cho em mét sè tiÒn ®óng b»ng sè tiÒn cña em, råi em l¹i cho anh mét sè tiÒn ®óng b»ng sè tiÒn cßn l¹i cña anh th× em cã 35000 ®ång vµ anh cã 30000 ®ång. Hái mÑ ®· cho mçi ng-êi bao nhiªu tiÒn ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 60
3. Cã ba hép bi A, B, C. LÇn ®Çu chuyÓn 10 bi tõ hép A sang hép B vµ 15 bi tõ hép C sang hép B. LÇn thø hai chuyÓn 6 bi tõ hép A sang hép B vµ 9 bi tõ hép B sang hép C. LÇn thø ba chuyÓn 20 bi tõ hép C sang hép A vµ 18 bi tõ hép B sang hép A. LÇn thø t- chuyÓn 9 bi tõ hép A sang hép B vµ 7 bi tõ hép C sang hép B, th× cuèi cïng hép A cã 190 bi, hép B cã 350 bi, hép C cã 280 bi. Hái lóc ®Çu mçi hép cã bao nhiªu bi ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 4. Mét ng-êi ra chî b¸n cam. LÇn thø nhÊt b¸n 1/2 sè cam céng thªm 1/2 qu¶. LÇn thø hai b¸n 1/2 sè cam cßn l¹i céng thªm 1/2 qu¶. LÇn thø ba b¸n 1/2 sè cam cßn l¹i céng thªm 1/2 qu¶. LÇn thø t- b¸n 1/2 sè cam cßn l¹i céng 1/2 qu¶ th× võa hÕt. TÝnh sè cam ng-êi ®ã ®em b¸n. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 5. (To¸n cæ). Mét tªn tham lam gÆp mét con quû ë c¹nh chiÕc cÇu. Tªn nµy than phiÒn vÒ nçi nghÌo khæ cña m×nh. Con quû nãi r»ng \" T«i cã thÓ gióp anh. Cø mçi lÇn anh ®i qua cÇu th× sè tiÒn cña anh sÏ ®-îc t¨ng gÊp ®«i; nh-ng ngay sau ®ã anh ph¶i tr¶ cho t«i 24 xu. B»ng lßng chø ?\". Tªn tham lam b»ng lßng nh- thÕ. Sau khi h¾n ®i qua cÇu ba lÇn th× thÊy trong tói cña m×nh kh«ng cßn mét xu nµo. Hái lóc ®Çu tªn tham lam cã bao nhiªu tiÒn ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 6. Trong mét buæi lao ®éng trång c©y ®Çu xu©n, líp 5A ®· chia sè c©y cho c¸c tæ lÇn l-ît nh- sau: Tæ Mét trång 20 c©y vµ 4/ 100 sè c©y cßn l¹i; Tæ Hai trång 21 c©y vµ 4/100 sè c©y cßn l¹i; Tæ Ba trång 22 c©y vµ 4/100 sè c©y cßn l¹i; …………………………………………………. Cø chia nh- vËy cho ®Õn tæ cuèi cïng th× võa hÕt sè c©y vµ sè c©y mçi tæ ®em trång ®Òu b»ng nhau. Hái líp 5 A cã mÊy tæ vµ mçi tæ ®-îc chia bao nhiªu c©y ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 7. Trong hép cã 130 bi. Hai b¹n ch¬i trß bèc bi. Mçi lÇn cã thÓ lÊy tõ 1 ®Õn 6 bi. Ai lÊy ®-îc viªn bi cuèi cïng ng-êi ®ã th¾ng cuéc. B¹n ®-îc bèc tr-íc, theo b¹n nªn lÊy nh- thÕ nµo ®Ó b¹n lu«n lµ ng-êi th¾ng cuéc ? .......................................................................................................................................................................... .......................................................................................................................................................................... 61
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DẠNG TOÁN CÔNG VIỆC Bài 1:Bác An làm một công việc hết 8 giờ .Bác Bình cũng công việc ấy hết 5 giờ .Hỏi nếu 2 bác cùng làm công việc ấy thi sau bao nhiêu giờ sẽ hoàn thành? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2: Nếu bể không có nước vòi thứ nhất chảy trong 3 giờ sẽ đầy bể.Nếu bể không có nước vòi thứ 2 chảy trong 5 giờ sẽ đầy bể .Hỏi nếu bể không có nước cùng 1 lúc cho cả 2 vòi chảy trì trong bao lâu sẽ đầy bể? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3: Bác Minh làm Một công việc hết 8 giờ .Bác Tâm cũng công việc ấy làm hết 5 giờ . Đầu tiên bác Minh làm một mình sau khi làm được 4 giờ thì bác Tâm đến làm cùng với bác Minh .Hỏi sau bao nhiêu lâu nữa thì hai bác làm xong công việc đó? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 4:Bác An làm một công việc hết 8 giờ .Bác Bình cũng công việc ấy hết 5 giờ .Lúc đâu 2 bác cùng làm nhưng sau khi làm được 3 giờ do bận công việc nên bác Bình phải đi làm việc khác .Hỏi bác An còn phải làm bao lâu nữa mới hoàn thành công việc ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 5: Nếu bể không có nước vòi thứ nhất chảy trong 4 giờ sẽ đầy bể.Nếu bể không có nước vòi thứ 2 chảy trong 5 giờ sẽ đầy bể .Khi bể không có nước người ta cho 2 vòi cùng chảy vào bể sau khi chảy được 2 giờ người ta tắt vòi thứ nhất để vòi thứ 2 chảy tiếp .Hỏi sau bao nhiêu thời gian nữa thì bể đầy nước? (Tham khảo thêm Đề thi và phần Bài tập mở rộng) .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................6..2.
Bài 1 : Sơn và Hải nhận làm chung một công việc. Nếu một mình Sơn làm thì sau 3 giờ sẽ xong việc, còn nếu Hải làm một mình thì sau 6 giờ sẽ xong công việc đó. Hỏi cả hai người cùng làm thì sau mấy giờ sẽ xong công việc đó. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2 : Hai vòi nước cùng chảy vào bể nước thì sau 1 giờ 12 phút sẽ đầy bể. Nếu một mình vòi thứ nhất chảy thì sau 2 giờ sẽ đầy bể. Hỏi nếu một mình vòi thứ hai chảy thì mấy giờ đầy bể ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 3 : Ba người dự định đắp xong một con đường. Người thứ nhất có thể đắp xong con đường đó trong 3 tuần. Người thứ hai có thể đắp xong một con đường dài gấp 3 lần con đường đó trong 8 tuần. Người thứ ba có thể đắp xong một con đường dài gấp 5 lần con đường đó trong 12 tuần. Hỏi cả ba người cùng đắp con đường dự định ban đầu thì sẽ hoàn thành trong bao nhiêu giờ, nếu mỗi tuần làm việc 45 giờ ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 63
19.BÀI TOÁN CHIA GIA TÀI *Đề : Một ông nhà giàu khi vợ đang mang thai thì mắc bệnh hiểm nghèo, trước lúc lâm chung ông ta để lại “Di chúc ” : Sau khi qua đời nếu vợ sinh con trai thì gia tài cho con trai 2/3 và vợ 1/3; Nếu sinh con gái thì con gái 1/3; vợ 1/3; còn lại 1/3 làm từ thiện. Nhưng thực tế sau khi ông ta chết, vọ sinh đôi : 1 con trai và 1 con gái. Hỏi Tòa án dân sự phải xử chia gia tài cho họ như thế nào ? Mỗi người được hưởng bao nhiêu phần ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... *Đề : Một ông nhà giàu khi vợ đang mang thai thì mắc bệnh hiểm nghèo, trước lúc lâm chung ông ta để lại “Di chúc ” : Sau khi qua đời nếu vợ sinh con trai thì gia tài cho con trai 2/3 và vợ 1/3; Nếu sinh con gái thì con gái 1/3; vợ 1/3; còn lại 1/3 làm từ thiện. Nhưng thực tế sau khi ông ta chết, vọ sinh đôi : 1 con trai và 1 con gái. Hỏi Tòa án dân sự phải xử chia gia tài cho họ như thế nào ? Mỗi người được hưởng bao nhiêu phần ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 64
20.DÙNG SƠ ĐỒ DIỆN TÍCH ĐỂ GIẢI TOÁN BA ĐẠI LƯỢNG Bài 1: Một ôtô đi từ Vinh đến Hà Nội dự định đi với vận tốc 30 km/h. Nhưng do trời mưa nên chỉ đi được 25 km/h, nên đến Hà Nội muộn mất 2 giờ so với thời gian dự định. Tính quãng đường Vinh - Hà Nội? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 2: Bố bạn An năm nay 30 tuổi. Nếu lấy số tuổi bố bạn An cách đây 5 năm và số tuổi của An bây giờ cộng với 2 rồi nhân hai số đó với nhau thì cũng bằng số tuổi bố bạn An bây giờ nhân với số tuổi bạn An bây giờ. Tính tuổi bạn An bây giờ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 65
TOÁN 4 – HỌC KÌ 2 NÂNG CAO THEO CHỦ ĐỀ ph©n sè 21/ph©n sè - RÚT GỌN PHÂN SỐ Bài 137: Viết các phân số sau theo thứ tự từ bé đến lớn: 4 ; 3 ; 6 777 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 141: So sánh a) 3 + 2 b) 3 7 c) 8 9 44 88 10 10 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 149: Khu đất nhà Lan có 3 diện tích đất làm nhà, 2 diện tích dùng để trồng rau. Hỏi: 57 a)Diện tích đất làm nhà và trồng rau bằng bao nhiêu phần diện tích của khu vườn? a) Diện tích làm nhà nhiêu hơn diện tích trồng rau bao nhiêu phần diện tích khu đất? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 150: Tìm x a) x 3 4 b) 7 x 3 c) x 3 9 d) 9 x 2 43 12 2 11 22 29 66
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Bài 151: Trong số các bài kiểm tra giữa kì II của khối lớp 4, có 3 số bài đạt điểm khá. Biết số bài đạt 7 29 điểm khá và giỏi là 35 số bài kiểm tra. Hỏi số bài đạt điểm giỏi chiếm bao nhiêu phân số bài kiểm tra? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 154: T×m sè tù nhiªn x sao cho: 4 x 5 7 10 7 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 155: T×m hai ph©n sè biÕt r»ng hai ph©n sè ®ã ®Òu cã mÉu sè lµ 8, c¸c tö sè cÇn t×m lµ hai sè tù nhiªn liªn tiÕp vµ ph©n sè 3 n»m gi÷a hai ph©n sè ®ã. 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 156: T×m hai ph©n sè biÕt r»ng hai ph©n sè ®ã ®Òu cã tö sè lµ 1, c¸c mÉu sè ph¶i t×m lµ hai sè tù nhiªn liªn tiÕp vµ ph©n sè 13 n»m gi÷a hai ph©n sè ®ã. 84 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 67
22/So s¸nh ph©n sè Bµi 1: So s¸nh c¸c ph©n sè sau b»ng c¸ch hîp lÝ nhÊt: a) 12 vµ 7 d) 1998 vµ 1999 PhÇn bï 17 15 1999 2000 b) 1999 vµ 12 So s¸nh víi 1 2001 11 c) 13 vµ 27 PhÇn bï g) 23 vµ 24 ( Trung gian) 27 41 47 45 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 2: So s¸nh c¸c ph©n sè sau b»ng c¸ch hîp lÝ nhÊt: a) 15 vµ 5 PhÇn bï d) 3 vµ 17 SS víi 15/49 25 7 8 49 b) 13 vµ 27 Trung gian26/120 e) 47 vµ 29 ( TS > MS) 60 100 15 35 c) 1993 vµ 997 (997x2) SS phÇn bï g) 16 vµ 15 SS 16/29 1995 998 27 29 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 3: So s¸nh c¸c ph©n sè sau b»ng c¸ch hîp lÝ nhÊt: a) 13 vµ 23 (SS phÇn bï) c) 12 vµ 25 SS 24/49 15 25 25 49 b) 23 vµ 24 SS Trung gian 28 27 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 157: So s¸nh b»ng c¸ch hîp lÝ 3 vµ 33 ; 1313 vµ 13 b) 22 vµ 11 c) 13 vµ 7 d) 2007 vµ 2006 a) 8 2 2006 2008 7 77 1414 14 11 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 158: Kh«ng quy ®ång mÉu sè h·y so s¸nh c¸c ph©n sè a) 2007 vµ 2008 b) 2 vµ 3 c) 2 vµ 3 d) 5 vµ 2 e) 5 vµ 9 g) 77 vµ 78 2008 2009 3 4 13 14 14 11 6 10 78 79 h) 17 vµ 18 i) 20 vµ 21 18 19 21 22 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 159: So s¸nh b»ng c¸ch hîp lÝ a) 97 vµ 96 b) 2007 vµ 2005 c) 2007 vµ 2008 d) 25 vµ 24 96 95 2006 2004 2006 2007 24 23 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 160: Kh«ng quy ®ång mÉu sè h·y so s¸nh a) 4 vµ 3 b) 11 vµ 13 c) 45 vµ 47 d) 20 vµ 19 e) 45 vµ 44 9 10 19 18 97 96 31 33 46 47 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 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Bµi 161: H·y chøng tá r»ng c¸c ph©n sè sau b»ng nhau 7 77 777 b) 123 123123 c) 13 1313 131313 a) 9 99 999 127 127127 15 1515 151515 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 162: So s¸nh c¸c ph©n sè sau víi 1 a) 34 34 b) 19911999 33 35 1995 1995 .......................................................................................................................................................................... .......................................................................................................................................................................... 75
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Bµi 163: So s¸nh c¸c ph©n sè sau (víi n lµ sè tù nhiªn) n 1 vµ n3 b) n vµ n 1 a) n3 n4 n2 n4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 164: So s¸nh c¸c ph©n sè sau(a lµ sè tù nhiªn kh¸c 0) a) a 1 vµ a 3 b) a vµ a 1 a a2 a6 a7 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 23/ TÌM PHÂN SỐ CỦA MỘT SỐ Bài 165: Lớp 4A có 27 học sinh, trong đó số bạn nữ bằng 2 số học sinh cả lớp. Tìm số học sinh nam? 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 166: Lớp 4B có 10 bạn nữ, số bạn nam bằng 3 số bạn nữ. Tìm số bạn nam? 2 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 167: Một sân trường hình chữ nhật có chiều rộng bằng 90m, chiều dài bằng 4 chiều rộng. Tính 3 diện tích sân trường đó. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 76
.......................................................................................................................................................................... .......................................................................................................................................................................... Bài 168: Nam có 27 viên bi gồm hai màu vàng và đỏ, trong đó số bi màu vàng bằng 2 tổng số bi. Tìm số 3 bi màu đỏ? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 169: An có 10 quyển vở, Bình có số vở bằng 3 số vở của An. Bình có bao nhiêu quyển vở? 2 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bài 170: Một sân trường hình chữ nhật có chiều dài bằng 90m, chiều rộng bằng 2 chiều dài. Tính diện 3 tích sân trường đó. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 171: C¶ 3 ng-êi thî lµm c«ng ®-îc 270 000 ®ång. Ng-êi thø nhÊt ®-îc 1 sè tiÒn, ng-êi thø hai ®-îc 2 2 sè tiÒn. TÝnh tiÒn cña ng-êi thø ba. 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 17 2: Hai ng-êi chia nhau 720 000 ®ång. Ng-êi thø nhÊt ®-îc 1 sè tiÒn, ng-êi thø hai ®-îc 1 sè 68 tiÒn, sè tiÒn cßn l¹i lµ cña ng-êi thø ba. Hái ng-êi thø ba ®-îc bao nhiªu tiÒn? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 77
Bµi 1: C¶ ba ng-êi thî lµm c«ng ®-îc 270000 ®ång. Ng-êi thø nhÊt ®-îc 1 sè tiÒn. Ng-êi thø hai ®-îc 3 2 sè tiÒn. TÝnh sè tiÒn cña ng-êi thø ba. 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 2: Hai ng-êi chia nhau 720000 ®ång. Ng-êi thø nhÊt ®-îc 1 sè tiÒn. Ng-êi thø hai ®-îc 1 sè tiÒn. 68 Sè tiÒn cßn l¹i lµ cña ng-êi thø ba. Hái ng-êi thø ba ®-îc chia bao nhiªu tiÒn? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: Ba b¹n chia nhau 30 qu¶ cam. Nam lÊy 2 sè cam, Ph-îng lÊy sè cam b»ng 4 sè cam cña Mai. 55 Hái mçi b¹n ®-îc bao nhiªu qu¶ cam? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Hai anh em cã tÊt c¶ 40 viªn bi, biÕt 1 sè bi cña em b»ng 1 sè bi cña anh. TÝnh sè bi cña mçi 35 ng-êi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: HiÖn nay mÑ h¬n con 24 tuæi, biÕt 1 tuæi cña con b»ng 1 tuæi cña mÑ.TÝnh tuæi cña mçi ng-êi. 3 11 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 78
.......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Líp 5A cã 1 sè häc sinh n÷ b»ng 1 sè häc sinh nam. BiÕt sè häc sinh n÷ kÐm sè häc sinh nam lµ 25 15 b¹n. TÝnh sè häc sinh n÷ vµ sè häc sinh nam. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 7: Líp 5A cã 35 häc sinh, biÕt 1 sè häc sinh nam b»ng 1 sè häc sinh n÷. TÝnh sè häc sinh nam vµ 52 häc sinh n÷. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: Ba khu vùc A, B, C cã tæng sè d©n lµ 12000 ng-êi. TÝnh sè d©n mçi khu vùc, biÕt 2 sè d©n khu 3 vùc A b»ng 5 sè d©n khu vùc B vµ b»ng 4 sè d©n khu vùc C. 10 10 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: Hai anh em ®i mua s¸ch hÕt 112000 ®ång. BiÕt 3 sè tiÒn s¸ch cña em b»ng 1 sè tiÒn cña anh. Hái 53 mçi ng-êi mua hÕt bao nhiªu tiÒn s¸ch? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 79
24/ t×m sè khi biÕt gi¸ trÞ mét ph©n sè cña nã Bµi 1: Mét xe m¸y ngµy thø nhÊt ®i ®-îc 2 qu·ng ®-êng, ngµy thø hai ®i 5 ®-îc 1 qu·ng ®-êng, ngµy thø ba ®i thªm 40km n÷a th× võa hÕt qu·ng ®-êng. Hái qu·ng ®- 3 êng xe m¸y ®i trong ba ngµy lµ bao nhiªu ki-l«-mÐt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 1 sè v¶i, lÇn thø hai b¸n 1 sè v¶i th× cßn l¹i 7m. Hái Bµi 2: Mét ng-êi b¸n hµng v¶i, lÇn thø nhÊt b¸n 2 3 tÊm v¶i ®ã dµi bao nhiªn mÐt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 80
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: Mét bÇy ong ®i t×m mËt, 1 sè ong bay ®Õn v-ên nh·n, 1 sè ong bay ®Õn v-ên hång, cßn l¹i 5 con 23 ®ang bay ®Õn v-ên xoµi. Hái bÇy ong ®ã cã bao nhiªu con? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Tæng sè tuæi cña ba cha con lµ 85 tuæi. Tuæi con g¸i b»ng 2 tuæi bè, tuæi cña con trai b»ng 3 tuæi 54 cña con g¸i. TÝnh tuæi cña mçi ng-êi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: Ba thïng ®ùng 52 lÝt x¨ng. Thïng thø nhÊt ®ùng b»ng 1 thïng thø ba, thïng thø hai ®ùng b»ng 2 23 thïng thø ba. TÝnh xem mçi thïng ®ùng bao nhiªu lÝt x¨ng? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Mét cöa hµng b¸n tÊm v¶i lµm ba lÇn. LÇn thø nhÊt b¸n 1 tÊm v¶i vµ 5m, lÇn thø hai b¸n 3 sè v¶i 37 cßn l¹i vµ 3m, lÇn thø ba b¸n 17m v¶i th× võa hÕt. Hái lÇn mét, lÇn hai mçi lÇn b¸n bao nhiªu mÐt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... LuyÖn tËp Bµi 2: Mét ng-êi b¸n hµng, lÇn mét b¸n 1 sè trøng , lÇn thø hai b¸n 3 sè trøng th× cßn l¹i 17 qu¶. Hái 58 ng-êi ®ã ®em b¸n bao nhiªu qu¶ tr-ng vµ mçi lÇn b¸n bao nhiªu qu¶? 81
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Bµi 3: Mét gi¸ s¸ch cã 3 ng¨n, biÕt sè s¸ch ë ng¨n thø nhÊt b»ng 2 sè s¸ch ë ng¨n thø ba, sè s¸ch ë ng¨n 3 thø hai b»ng 3 sè s¸ch ë ng¨n thø nhÊt. BiÕt ng¨n thø thø ba nhiÒu h¬n ng¨n thø hai lµ 45 quyÓn. 4 TÝnh sè s¸ch ë mçi ng¨n. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Nhãm thî gÆt thø nhÊt gÆt ®-îc 3 diÖn tÝch thöa ruéng. Nhãm thî gÆt thø hai gÆt ®-îc 2 diÖn tÝch 85 thöa ruéng. Nhãm hai gÆt nhiÒu h¬n nhãm mét lµ 100m2. TÝnh diÖn tÝch mçi nhãm gÆt ®-îc. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: Ba ®µn gµ, ®µn gµ thø nhÊt b»ng 4 ®µn gµ thø hai. §µn gµ thø ba b»ng 4 ®µn gµ thø hai. §µn thø 36 nhÊt nhiÒu h¬n ®µn gµ thø ba 24 con. Hái mçi ®µn cã bao nhiªu con? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Mét « t« ®i trong 2 ngµy ®-îc 13 qu·ng ®-êng. Ngµy thø 2 ®i ®-îc 5 qu·ng ®-êng vµ ®i nhiÒu 14 7 h¬n ngµy thø nhÊt 35km. Hái mçi ngµy « t« ®i ®-îc bao nhiªu ki-l«-mÐt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 82
Bµi 7: Mai vµ Hång ®i mua s¸ch. Sau khi mua mai mua hÕt 3 sè tiÒn mang ®i, Hång tiªu hÕt 2 sè tiÒn 43 Hång mang ®i th× c¶ hai cßn l¹i 20600®ång, Trong ®ã Mai cßn nhiÒu h¬n Hång 600®ång. Hái mçi b¹n mang ®i bao nhiªu tiÒn? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: ChÞ T- mang ®i chî mét ræ cam. LÇn ®Çu chÞ b¸n ®-îc 2 sè cam, lÇn sau chÞ b¸n ®-îc 3 sè cam 54 cßn l¹i. Sau hai lÇn b¸n chÞ cßn l¹i 21 qu¶ cam. Hái ræ cam ban ®Çu cã bao nhiªu qu¶? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: Ng-êi l¸i xe tr-íc khi ®i thÊy chØ cßn 3 thïng x¨ng, sî kh«ng ®ñ ng-êi ®ã mua thªm 15 lÝt x¨ng 5 n÷a. Khi vÒ tíi nhµ anh thÊy chØ cßn 3 thïng x¨ng vµ tÝnh ra xe tiªu thô hÕt 30 lÝt x¨ng trong 10 chuyÕn ®i ®ã. Hái thïng x¨ng chøa bao nhiªu lÝt x¨ng? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 10: Ba anh em Nam, H¶i, TÊn ®-îc mÑ cho mét sè tiÒn . Nam ®-îc 1 sè tiÒn, H¶i ®-îc 2 sè tiÒn, sè 45 tiÒn cßn l¹i lµ cña TÊn. Hái mçi ng-êi ®-îc mÑ cho bao nhiªu tiÒn, biÕt sè tiÒn mÑ cho TÊn h¬n Nam 6000®ång? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 12: §Çu xu©n Êt DËu gia ®×nh b¸c An nu«i 268 con gµ gåm 3 lo¹i: gµ vµng, gµ tr¾ng, gµ khoang. BiÕt sè gµ tr¾ng b»ng 5 sè gµ vµng, sè gµ khoang b»ng 7 sè gµ tr¾ng. TÝnh sè gµ mçi lo¹i. 69 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 83
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 13: Ba xe chë g¹o lªn nói 1 sè g¹o chë trªn xe thø nhÊt b»ng 1 sè g¹o chë trªn xe 43 thø 2 vµ b»ng 1 sè g¹o chë trªn xe thø 3. Xe thø 3 chë nhiÒu h¬n xe thø 2 lµ 6 tÊn. Hái mçi xe 5 chë bao nhiªu tÊn g¹o? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 14: Cóc võa ®-îc th-ëng mét sè tiÒn. Cóc lÊy 3 sè tiÒn ®em ®i chî, Cóc ®· mua hÕt 2 sè tiÒn mang 53 ®i. Sè tiÒn cßn l¹i Cóc ®em vÒ 27 000 ®ång. Hái sè tiÒn Cóc ®-îc th-ëng lµ bao nhiªu? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 15: Mét to¸n c«ng nh©n nhËn lµm mét ®o¹n ®-êng trong 3 tuÇn. TuÇn ®Çu lµm ®-îc 2 5 ®o¹n ®-êng. TuÇn thø 2 lµm ®-îc ®o¹n ®-êng b»ng 2 tuÇn ®Çu. TuÇn thø 3 lµm ®-îc 450m th× 3 hÕt ®o¹n ®-êng. Hái: a) §o¹n ®-êng dµi bao nhiªu mÐt? b) Hai tuÇn ®Çu, mçi tuÇn lµm ®-îc bao nhiªu mÐt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 84
25. T×m hai sè khi biÕt tæng vµ tØ sè cña hai sè ®ã Bµi 1: MÑ em tr¶ hÕt tÊt c¶ 84600 ®ång ®Ó mua mét sè tr¸i c©y gåm cam, t¸o vµ lª. T¸o gi¸ 2100 ®ång 1 qu¶, cam gi¸ 1600 ®ång 1 qu¶ vµ lª gi¸ 3500 ®ång mét qu¶. BiÕt mÑ em ®· mua sè cam b»ng 2 lÇn sè t¸o vµ sè t¸o b»ng 2 lÇn sè lª. T×m sè qu¶ mçi lo¹i mÑ em ®· mua. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 2: Mét cöa hµng rau qu¶ cã 185,5kg chanh vµ cam. Sau khi b¸n, ng-êi b¸n hµng thÊy r»ng: l-îng chanh ®· b¸n b»ng 1 l-îng cam ®· b¸n vµ l-îng chanh cßn l¹i nhiÒu h¬n l-îng cam cßn l¹i 4 17,5kg. Hái cöa hµng ®ã ®· b¸n ®-îc bao nhiªu ki - l« - gam mçi lo¹i, biÕt r»ng ban ®Çu sè chanh b»ng 2 sè cam? 3 85
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: Mét cöa hµng cã 215,5kg g¹o tÎ vµ g¹o nÕp. L-îng g¹o nÕp ®· b¸n b»ng 1 l-îng g¹o tÎ ®· b¸n. 4 Sau khi b¸n, l-îng g¹o nÕp cßn l¹i h¬n l-îng g¹o tÎ cßn l¹i lµ 25,9kg. Hái cöa hµng ®· b¸n bao nhiªu ki - l« - gam mçi lo¹i, biÕt r»ng ban ®Çu g¹o nÕp b»ng 2 g¹o tÎ? 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Mét cöa hµng rau qu¶ cã hai ræ ®ùng cam vµ chanh. Sau khi b¸n, 4 sè cam vµ 5 sè chanh th× 79 ng-êi b¸n hµng thÊy cßn l¹i 160 qu¶ hai lo¹i. Trong ®ã sè cam b»ng 3 sè chanh. Hái lóc ®Çu cöa 5 hµng cã bao nhiªu qu¶ mçi lo¹i? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: Ba líp cïng gãp b¸nh ®Ó liªn hoan cuèi n¨m. Líp A gãp 5kg b¸nh, líp B gãp 3kg b¸nh cïng lo¹i. Sè b¸nh ®ã ®ñ dïng cho c¶ 3 líp nªn líp C kh«ng ph¶i mua b¸nh mµ ph¶i tr¶ cho 2 líp kia lµ 24000 ®ång. Hái mçi líp A, B nhËn ®-îc bao nhiªu tiÒn? (Mçi líp gãp sè tiÒn nh- nhau). .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Tuæi vµ th¬ gãp b¸nh ¨n chung, Tuæi gãp 3 chiÕc, Th¬ gãp 5 chiÕc. Võa lóc ®ã, To¸n ®i tíi. Tuæi vµ Th¬ mêi To¸n ¨n cïng. ¡n xong To¸n tr¶ l¹i cho 2 b¹n 8000 ®ång. Hái Tuæi vµ Th¬ mçi ng-êi nhËn ®-îc bao nhiªu tiÒn? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 86
.......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 7: Trong thóng cã 150 qu¶ trøng gµ vµ trøng vÞt. MÑ ®· b¸n mçi lo¹i 15 qu¶. TÝnh ra sè trøng gµ cßn 2 sè trøng vÞt cßn l¹i. Hái lóc ®Çu trong thóng cã bao nhiªu trøng gµ, bao nhiªu trøng l¹i b»ng 5 vÞt? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: Trong thóng cã 210 qu¶ quýt vµ cam. MÑ ®· b¸n 60 qu¶ quýt. Lóc nµy, trong thóng cã sè quýt cßn l¹i b»ng 2 sè cam. Hái lóc ®Çu sè cam b»ng bao nhiªu phÇn sè quýt? 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: B¹n B×nh cã 22 viªn bi gåm bi ®á vµ bi xanh. B×nh cho em 3 viªn bi ®á vµ 2 viªn bi xanh. B¹n An l¹i cho B×nh thªm 7 viªn bi ®á n÷a. Lóc nµy, B×nh cã sè bi ®á gÊp ®«i sè bi xanh. Hái lóc ®Çu B×nh cã bao nhiªu viªn bi ®á, bao nhiªu viªn bi xanh? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 10: Trong mét khu v-ên, ng-êi ta trång tæng céng 120 c©y gåm 3 lo¹i: cam, chanh vµ xoµi. BiÕt sè cam b»ng 2 tæng sè chanh vµ xoµi, sè xoµi b»ng 1 tæng sè chanh vµ sè cam. Hái mçi l¹i cã bao 35 nhiªu c©y? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 11: Dòng cã 48 viªn bi gåm 3 lo¹i: bi xanh, bi ®á vµ bi vµng. Sè bi xanh b»ng tæng sè bi ®á vµ bi vµng, sè bi xanh céng sè bi ®á gÊp 5 lÇn sè bi vµng. Hái mçi lo¹i cã bao nhiªu viªn bi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 87
.......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 14: Ngµy xu©n 3 b¹n: HuÖ, H»ng, Mai ®i trång c©y. BiÕt r»ng tæng sè c©y cña 3 b¹n trång ®-îc lµ 17 c©y. Sè c©y cña 2 b¹n HuÖ vµ H»ng trång ®-îc nhiÒu h¬n Mai trång lµ 3 c©y. Sè c©y cña HuÖ trång ®-îc b»ng 2 sè c©y cña H»ng. Em h·y tÝnh xem mçi b¹n trång ®-îc bao nhiªu c©y? 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 173: T×m hai sè cã tæng b»ng 80. BiÕt sè bÐ b»ng 2 sè lín 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 174: T×m hai sè cã trung b×nh céng b»ng 108, biÕt th-¬ng cña hai sè ®ã b»ng 5. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 175: T×m hai sè cã trung b×nh céng b»ng 231, biÕt r»ng nÕu thªm mét ch÷ sè 0 vµo bªn ph¶i sè bÐ th× ®-îc sè lín. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 176: Hai thïng dÇu cã tæng céng 126 lÝt, biÕt sè dÇu ë thïng thø nhÊt b»ng 5 sè dÇu ë thïng thø hai. 2 Hái mçi thïng cã bao nhiªu lÝt dÇu? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 177: Dòng vµ Minh cã tæng céng 55 viªn bi, biÕt r»ng nÕu Dòng cho Minh 5 viªn bi th× sè bi cña Minh sÏ b»ng 4 sè bi cña Dòng. Hái mçi b¹n cã bao nhiªu viªn bi? 7 .......................................................................................................................................................................... .......................................................................................................................................................................... 88
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 178: Hång vµ Lan cã tæng céng 40 quyÓn vë. 3 lÇn sè vë cña Hång th× b»ng 2 lÇn sè vë cña Lan. Hái mçi b¹n cã bao nhiªu vë? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 179: Hép bi gåm hai lo¹i xanh vµ ®á, cã tæng céng 49 viªn bi, biÕt r»ng 1 sè bi xanh b»ng 1 sè bi 34 ®á. Hái mçi lo¹i cã bao nhiªu viªn bi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 180: Mét trang tr¹ing-êi ta nu«i mét sè ®µn gia sóc cã 104 con gåm hai lo¹i tr©u vµ bß, biÕt r»ng 3 lÇn sè tr©u th× b»ng 5 lÇn sè bß. Hái trang tr¹i ®ã cã bao nhiªu con tr©u, bao nhiªu con bß? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 181: T×m hai sè cã tæng b»ng 295, biÕt r»ng nÕu lÊy sè lín chia cho sè bÐ th× ®-îc th-¬ng lµ 8 vµ sè d- lµ 7. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 182: Tæng sè tuæi cña hai «ng ch¸u lµ 65 tuæi, biÕt tuæi ch¸u bao nhiªu th¸ng th× tuæi «ng bÊy nhiªu n¨m. Hái «ng bao nhiªu tuæi, ch¸u bao nhiªu tuæi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 183: HiÖn nay tuæi bè gÊp 4 lÇn tuæi con,biÕt r»ng 5 n¨m n÷a th× tæng sè tuæi cña hai bè con lµ 55 tuæi. Hái hiÖn nay bè bao nhiªu tuæi? con bao nhiªu tuæi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 89
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 184: Tr-íc ®©y lóc tuæi anh b»ng tuæi em hiÖn nay th× tuæi anh gÊp ®«i tuæi em, hiÖn nay tæng sè tuæi cña hai anh em lµ 20 tuæi. Hái hiÖn nay anh bao nhiªu tuæi, em bao nhiªu tuæi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 26. T×m hai sè khi biÕt hiÖu vµ tØ sè cña hai sè ®ã Bµi 1: N¨m nay con 25 tuæi, nÕu tÝnh sang n¨m th× tuæi cha gÊp 2 lÇn tuæi con hiÖn nay. Hái lóc cha bao nhiªu tuæi th× tuæi con b»ng 1 tuæi cha? 4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 90
Bµi 2: Mét líp cã 1 sè häc sinh nam b»ng 1 sè häc sinh n÷. Sè häc sinh nam Ýt h¬n sè häc sinh n÷ 12 35 b¹n. TÝnh sè häc sinh nam, sè häc sinh n÷ cña líp ®ã. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: Cho mét ph©n sè cã tæng cña tö sè vµ mÉu sè lµ 4013 vµ mÉu sè lín h¬n tö sè lµ 1. a) H·y t×m ph©n sè ®ã. b) NÕu céng thªm 4455332 vµo tö sè th× ph¶i céng thªm vµo mÉu sè bao nhiªu ®Ó gi¸ trÞ cña ph©n sè kh«ng thay ®æi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Khi anh t«i 9 tuæi th× mÑ míi sinh ra t«i. Tr-íc ®©y, lóc mµ tuæi anh t«i b»ng tuæi t«i hiÖn nay th× t«i chØ b»ng 2 tuæi anh t«i. §è b¹n tÝnh ®-îc tuæi cña anh t«i hiÖn nay. 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: Mét cöa hµng cã sè bót ch× xanh gÊp 3 lÇn sè bót ch× ®á. Sau khi cöa hµng b¸n ®i 12 bót ch× xanh vµ 7 bót ch× ®á th× phÇn cßn l¹i sè bót ch× xanh h¬n sè bót ch× ®á lµ 51 c©y. Hái tr-íc khi b¸n mçi lo¹i bót ch× cã bao nhiªu chiÕc? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Lõa vµ Ngùa cïng chë hµng. Ngùa nãi: “NÕu anh chë gióp t«i 2 bao hµng th× 2 chóng ta chë b»ng nhau”. Lõa nãi l¹i víi Ngùa: “Cßn nÕu anh chë gióp t«i 2 bao hµng th× anh sÏ chë gÊp 5 lÇn t«i”. Hái mçi con chë bao nhiªu bao hµng? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 91
Bµi 7: BiÕt 1 tuæi An c¸ch ®©y 6 n¨m b»ng 1 tuæi An 6 n¨m tíi. Hái hiÖn nay An bao nhiªu tuæi? 25 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: Cho mét sè tù nhiªn. NÕu thªm 28 ®¬n vÞ vµo 1 sè ®ã ta ®-îc sè míi gÊp 2 lÇn sè cÇn t×m. T×m sè 4 tù nhiªn ®ã. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: T×m hai sè cã hiÖu b»ng 252, biÕt sè bÐ b»ng 1 tæng 2 sè ®ã. 4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 10: T×m 2 sè cã hiÖu b»ng 310, biÕt 2 sè thø hai gÊp 4 lÇn sè thø nhÊt. 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 11: T×m sè A, biÕt 4 lÇn sè A h¬n 1 sè A lµ 2025 ®¬n vÞ. 4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 184: T×m hai sè cã hiÖu b»ng 516, biÕt r»ng nÕu lÊy sè lín chia cho sè bÐ th× ®-îc th-¬ng b»ng 4. .......................................................................................................................................................................... .......................................................................................................................................................................... 92
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Bµi 185:T×m hai sè biÕt tØ sè cña chóng b»ng 4 vµ nÕu lÊy sè lín trõ ®i sè bÐ th× ®-îc kÕt qu¶ b»ng 360. 7 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 186:T×m hai sè cã hiÖu b»ng 333, biÕt r»ng nÕu viÕt thªm mét ch÷ sè 0 vµo bªn ph¶i sè bÐ th× ®-îc sè lín. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 187: T×m hai sè cã tØ sè lµ 1 , biÕt r»ng sè lín lµ sè cã ba ch÷ sè vµ nÕu xãa ch÷ sè 4 ë hµng tr¨m cña 9 sè lín th× ®-îc sè bÐ. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 188: T×m hai sè cã hiÖu b»ng 165, biÕt r»ng nÕu lÊy sè lín chia cho sè bÐ th× ®-îc th-¬ng lµ 7 vµ cã sè d- lµ 3. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 189: HiÖn nay bè 32 tuæi, em 5 tuæi. Hái bao nhiªu n¨m n÷a tuæi cña bè gÊp 5 lÇn tuæi cña con. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 190 : T×m hai sè cã hiÖu b»ng 216, biÕt r»ng nÕu thªm mét ch÷ sè 0 vµo bªn ph¶i sè bÐ th× ®-îc sè lín. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 93
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Bµi 191: HiÖu cña hai sè b»ng 393, biÕt r»ng nÕu xo¸ ch÷ sè cuèi cña sè lín th× ®-îc sè bÐ. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 192: HiÖn nay bè 31 tuæi, con 4 tuæi. Hái bao nhiªu n¨m n÷a tuæi bè gÊp 4 lÇn tuæi con? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 193: BiÕt 1 tuæi Thanh håi 6 n¨m tr-íc b»ng 1 tuæi cña Thanh 6 n¨m tíi. Hái hiÖn Thanh bao nhiªu 25 tuæi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 194: HiÖn nay tæng sè tuæi cña hai bµ ch¸u lµ 72 tuæi, tuæi bµ gÊp 5 lÇn tuæi ch¸u. Hái c¸ch nay mÊy n¨m tuæi bµ gÊp 9 lÇn tuæi ch¸u? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 195: HiÖn nay tuæi mÑ gÊp 4 lÇn tuæi con, tr-íc ®©y 6 n¨m tuæi mÑ gÊp 13 lÇn tuæi con. Hái hiÖn nay mÑ bao nhiªu tuæi? Con bao nhiªu tuæi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 27. t×m mét sè khi biÕt “Hai tØ sè” Bµi 1: Mét gi¸ s¸ch cã hai ng¨n, sè s¸ch ë ng¨n d-íi b»ng 5 sè s¸ch ë ng¨n trªn. NÕu ng¨n d-íi bít ®i 6 11 quyÓn th× sè s¸ch ng¨n d-íi b»ng 4 sè s¸ch ë ng¨n trªn. Hái trªn gi¸ cã bao nhiªu quyÓn 7 s¸ch? 94
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Bµi 2: Líp 5A cã sè häc sinh b»ng 1 sè häc sinh cña líp. NÕu líp 5A bít ®i 2 b¹n n÷ th× sè häc sinh n÷ 3 b»ng 1 sè häc sinh c¶ líp. Hái líp 5A cã bao nhiªu häc sinh? 4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: Líp 5A cã sè häc sinh n÷ b»ng 2 sè häc sinh nam. NÕu hai b¹n n÷ chuyÓn ®i vµ thay vµo ®ã lµ 3 hai b¹n nam th× sè häc sinh n÷ b»ng 4 sè häc sinh nam. T×m sè häc sinh líp 5A. 7 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: Mét gi¸ s¸ch gåm hai ng¨n. Sè s¸ch ë ng¨n d-íi b»ng 6 sè s¸ch ë ng¨n trªn. NÕu thªm 15 cuèn 5 s¸ch vµo ng¨n trªn th× sè s¸ch ë ng¨n trªn b»ng 11 sè s¸ch ë ng¨n d-íi. Hái gi¸ s¸ch cã bao 12 nhiªu quyÓn? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: Giê ra ch¬i, líp 5A cã sè häc sinh trong líp b»ng 1 sè häc sinh ngoµi 4 s©n. NÕu cã hai b¹n tõ trong líp ra s©n th× sè häc sinh trong líp b»ng 1 sè häc sinh ngoµi s©n. 5 TÝnh sè häc sinh líp 5A? .......................................................................................................................................................................... .......................................................................................................................................................................... 95
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: Giê ra ch¬i, líp 5A cã sè häc sinh trong líp b»ng 1 sè häc sinh ngoµi s©n. NÕu sè häc sinh trong 3 líp bít ®i 2 em vµ sè häc sinh ngoµi s©n gi÷ nguyªn th× sè häc sinh trong líp b»ng 1 sè häc sinh 4 ngoµi s©n. TÝnh sè häc sinh líp 5A? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 7: Giê ra ch¬i, líp 5B cã sè häc sinh trong líp b»ng 1 sè häc sinh ngoµi s©n. NÕu sè 3 häc sinh ngoµi s©n ®-îc t¨ng 12 em vµ gi÷ nguyªn sè häc sinh trong líp th× sè häc sinh trong líp b»ng 1 sè häc sinh ngoµi s©n. TÝnh sè häc sinh líp 5B? 4 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: Giê ra ch¬i, líp 5B cã sè häc sinh trong líp b»ng 1 sè häc sinh c¶ líp. NÕu sè häc 4 sinh trong líp bít ®i 2 em vµ gi÷ nguyªn sè häc sinh ngoµi s©n th× sè häc sinh trong líp b»ng 1 5 sè häc sinh c¶ líp. TÝnh sè häc sinh líp 5B? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: §Çu n¨m häc, sè ®éi viªn tr-êng em b»ng 1 sè häc sinh cßn l¹i cña tr-êng. §Õn cuèi häc k× I 3 tr-êng kÕt n¹p thªm 210 häc sinh vµo ®éi nªn sè häc sinh cßn l¹i cña tr-êng b»ng 2 sè ®éi viªn 3 cña tr-êng. Hái ®Õn cuèi häc k× I, sè ®éi viªn cña tr-êng lµ bao nhiªu em? BiÕt sè häc sinh cña tr-êng kh«ng thay ®æi. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 96
.......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 10: Mét ng-êi b¸n mét tÊm v¶i ®-îc l·i 1 gi¸ mua. NÕu ng-êi ®ã b¸n tÊm v¶i cao h¬n 40 000 ®ång 5 n÷a th× sè tiÒn l·i b»ng 1 gi¸ b¸n. Hái tÊm v¶i ®ã ®-îc b¸n víi gi¸ bao nhiªu tiÒn? 5 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 11: HiÖn nay, tuæi con b»ng 1 tuæi cha. Sau 15 n¨m n÷a th× tuæi con b»ng 2 tuæi cha. TÝnh tuæi cña 45 mçi ng-êi hiÖn nay? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 12: HiÖn nay tuæi mÑ gÊp 4 lÇn tuæi con. N¨m n¨m sau tuæi mÑ gÊp 3 lÇn tuæi con. TÝnh tuæi hiÖn nay cña mçi ng-êi? .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 28. Ph©n sè - tØ sè phÇn tr¨m Bµi 1: ViÕt tÊt c¶ c¸c ph©n sè b»ng ph©n sè 75 mµ mÉu sè lµ sè trßn chôc vµ cã 2 ch÷ sè. 100 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 97
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Bµi 2: ViÕt tÊt c¶ c¸c ph©n sè b»ng ph©n sè 21 mµ mÉu sè cã 2 ch÷ sè vµ chia hÕt cho 2 vµ 3. 39 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 3: ViÕt mçi ph©n sè sau thµnh tæng 3 ph©n sè cã tö sè lµ 1 nh-ng cã mÉu sè kh¸c nhau: 7 ; 3 ; 2 8 83 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 4: ViÕt mçi ph©n sè sau thµnh tæng 2 ph©n sè tèi gi¶n cã mÉu sè kh¸c nhau. a) 7 b) 13 12 27 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 5: a) ViÕt 5 p/s cã tö sè b»ng nhau mµ mçi ph©n sè ®Òu lín h¬n 4 nh-ng bÐ h¬n 1 5 b) ViÕt 5 p/s cã mÉu sè b»ng nhau vµ mçi p/s ®Òu bÐ h¬n 1 2 c) ViiÐt 3 p/s cã tö sè b»ng 1 mµ mçi p/s ®Òu lín h¬n 1 nh-ng bÐ h¬n 2 63 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 6: H·y viÕt mçi ph©n sè sau thµnh tæng c¸c ph©n sè cã tö sè b»ng 1 vµ mÉu sè kh¸c nhau. 31;15 ; 25 . 12 16 27 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 98
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Bµi 7: H·y viÕt tÊt c¶ c¸c ph©n sè cã tæng cña tö sè vµ mÉu sè b»ng 10. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 8: T×m: a) 1 cña 6m c) 1 cña 1 2 10 5 b) 1 cña 21kg d) 8 cña 3 7 94 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 9: BiÕt 1 sè häc sinh cña líp 3A b»ng 1 sè häc sinh cña líp 3B. H·y t×m tØ sè gi÷a sè häc sinh líp 3A 23 vµ häc sinh líp 3B. .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... Bµi 10: T×m sè häc sinh cña khèi líp 4, biÕt 1 sè häc sinh cña khèi líp 4 lµ 50 em. 3 .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 29. CÁC BÀI TOÁN VỀ CẤU TẠO SỐ Bµi 2. Rót gän c¸c ph©n sè sau: 99
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