Bai_tap_toan_4

["183. a) 28 v\u00b5 15 . b) 4 v\u00b5 21 ; 8 v\u00b5 42 . 36 36 7 7 14 14 c) 88 v\u00b5 8 ; 176 v\u00b5 16 . 11 11 22 22 184. b) 63 \u00d7 81 = 21 \u00d7 3 \u00d7 27 \u00d7 3 = 9 . 135 \u00d7 84 27 \u00d7 5 \u00d7 21 \u00d7 4 20 c) 1111 \u00d7 5 = 101 \u00d7 11 \u00d7 5 = 11 \u00d7 5 = 11 . 1515 \u00d7 7 101 \u00d7 15 \u00d7 7 3\u00d7 5 \u00d77 21 185. HD : a) Trong hai ph\u00a9n s\u00e8 5 v\u00b5 7 ph\u00a9n s\u00e8 7 l\u00edn h\u00acn ph\u00a9n s\u00e8 5 , v\u00d7 9 9 9 9 \u00ae\u00a9y l\u00b5 hai ph\u00a9n s\u00e8 c\u00e3 c\u00efng m\u00c9u s\u00e8 l\u00b5 9, m\u00b5 7 > 5 n\u00aan 7 > 5 . 9 9 b) Gi\u00b6i th\u00ddch t\u2212\u00acng t\u00f9 nh\u2212 tr\u00aan ta c\u00e3 5 < 9 . 14 14 186. a) 4 > 2 ; b) 6 < 9 ; c) 1 = 2 ; 9 9 11 11 2 4 d) 7 < 11 ; e) 29 > 19 ; g) 7 = 5 (v\u00d7 c\u00efng b\u00bbng 41). 12 12 24 24 28 20 187. a) 5 < 11 ; b) 4 < 3 ; c) 5 > 3 ; 6 12 7 4 98 d) 10 = 5 ; e) 10 > 10 ; g) 8 < 8. 14 7 9 11 15 9 188. HD : a) C\u00b8ch 1: 7 > 7 (so s\u00b8nh hai ph\u00a9n s\u00e8 c\u00efng t\u00f6 s\u00e8). 8 10 C\u00b8ch 2 : Quy \u00ae\u00e5ng m\u00c9u s\u00e8 ta \u00ae\u2212\u00eec 35 v\u00b5 28 . 40 40 Ta c\u00e3 : 35 > 28 n\u00aan 7 > 7 . 40 40 8 10 b) T\u2212\u00acng t\u00f9 ph\u00c7n a). Ta c\u00e3 : 16 > 16 . 5 7 99","c) C\u00b8ch 1 : 6 < 1 (Ph\u00a9n s\u00e8 6 c\u00e3 t\u00f6 s\u00e8 b\u00d0 h\u00acn m\u00c9u s\u00e8 n\u00aan 6 < 1) . 7 7 7 C\u00b8ch 2 : Quy \u00ae\u00e5ng m\u00c9u s\u00e8 6 v\u00b5 1 \u00ae\u2212\u00eec 6 v\u00b5 7 , m\u00b5 6 < 7 n\u00aan 6 < 7 , 7 7 7 7 7 t\u00f8c l\u00b5 6 < 1. 7 d) T\u2212\u00acng t\u00f9 ph\u00c7n c). Ta c\u00e3 : 15 > 1. 11 e) C\u00b8ch 1 : 4 < 1 v\u00b5 1 < 9 n\u00aan 4 < 9 . 9 4 9 4 C\u00b8ch 2 : Quy \u00ae\u00e5ng m\u00c9u s\u00e8 hai ph\u00a9n s\u00e8 4 v\u00b5 9 \u00ae\u2212\u00eec 16 v\u00b5 81 , m\u00b5 9 4 36 36 16 < 81 , v\u00cby 4 < 9 . 36 36 9 4 g) T\u2212\u00acng t\u00f9 ph\u00c7n e). Ta c\u00e3 : 11 > 10 10 11 189. a) 8 ; 9 ; 12 ; 24 . 25 25 25 25 b) 7 ; 7 ; 7 ; 7 . 26 9 8 3 c) Quy \u00ae\u00e5ng m\u00c9u s\u00e8 c\u00b8c ph\u00a9n s\u00e8 14 ; 23 ; 9 ; 3 \u00ae\u2212\u00eec 15 30 10 5 28 ; 23 ; 27 ; 18 . X\u00d5p c\u00b8c ph\u00a9n s\u00e8 m\u00edi t\u00d7m \u00ae\u2212\u00eec theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 30 30 30 30 \u00ae\u00d5n l\u00edn l\u00b5 : 18 ; 23 ; 27 ; 28 . V\u00cby c\u00b8c ph\u00a9n s\u00e8 \u00ae\u00b7 cho s\u00bep x\u00d5p 30 30 30 30 theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 \u00ae\u00d5n l\u00edn l\u00b5 : 3 ; 23 ; 9 ; 14 . 5 30 10 15 d) C\u00e3 th\u00d3 l\u00b5m t\u2212\u00acng t\u00f9 nh\u2212 ph\u00c7n c) ho\u00c6c nh\u00cbn x\u00d0t nh\u2212 sau : \u2022 5 hay 10 < 11 ; 11 < 11 (theo c\u00b8ch so s\u00b8nh hai ph\u00a9n s\u00e8 c\u00efng 9 18 18 18 15 t\u00f6 s\u00e8). 100","\u2022 M\u00b5 11 < 14 . 15 15 Ta c\u00e3 c\u00b8c ph\u00a9n s\u00e8 s\u00bep x\u00d5p theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 \u00ae\u00d5n l\u00edn l\u00b5 : 5 ; 11 ; 11 ; 14 . 9 18 15 15 190. HD : Quy \u00ae\u00e5ng m\u00c9u s\u00e8 hai ph\u00a9n s\u00e8 2 v\u00b5 3 \u00ae\u2212\u00eec 14 v\u00b5 15 . V\u00d7 5 7 35 35 14 < 15 n\u00aan 2 < 3. Nh\u2212 v\u00cby : S\u00e8 h\u00e4c sinh th\u00ddch t\u00cbp b\u00aci \u00ddt h\u00acn s\u00e8 h\u00e4c 35 35 5 7 sinh th\u00ddch \u00ae\u00b8 b\u00e3ng, t\u00f8c l\u00b5 ghi \u00a7 \u00f8ng v\u00edi ph\u00c7n c) c\u00dfn ghi S \u00f8ng v\u00edi ph\u00c7n a) v\u00b5 ph\u00c7n b). 191. HD : Ta c\u00e3 5 = 10 = 15 = 20 . M\u00b5 : 15 > 10 (t\u00f8c l\u00b5 5 > 1201) ; 10 < 15 7 14 21 28 21 21 7 14 14 (t\u00f8c l\u00b5 5 < 15 ) ; 10 = 10 (t\u00f8c l\u00b5 5 = 10 ) ; 20 > 15 (t\u00f8c l\u00b5 5 > 15 ). 7 14 14 14 7 14 28 28 7 28 V\u00cby : 5 < 15 . 7 14 Ch\u00f3 \u00fd : V\u00edi hai ph\u00a9n s\u00e8 kh\u00b8c 0 b\u00cat k\u00d7 bao gi\u00ea c\u00f2ng c\u00e3 th\u00d3 so s\u00b8nh \u00ae\u2212\u00eec, t\u00f8c l\u00b5 x\u00b8c \u00ae\u00denh \u00ae\u2212\u00eec ph\u00a9n s\u00e8 n\u00b5y l\u00edn h\u00acn (ho\u00c6c b\u00d0 h\u00acn, ho\u00c6c b\u00bbng) ph\u00a9n s\u00e8 kia. 192. a) 2 > 1 ; b) 2 <3 ho\u00c6c 1 < 3 ; c) 3 = 6. 9 9 10 10 10 10 5 10 Ch\u00f3 \u00fd : Ch\u00d8 c\u00c7n vi\u00d5t s\u00e8 2 ho\u00c6c s\u00e8 1 v\u00b5o \u00ab tr\u00e8ng trong ph\u00c7n b). 193. HD : a) V\u00edi x < 4 th\u00d7 x l\u00b5 c\u00b8c s\u00e8 1, 2, 3 (v\u00d7 1 < 4 ; 2 < 4 ; 3 < 4 ) . 5 5 5 5 5 5 5 5 b) V\u00edi x < 2 th\u00d7 x l\u00b5 s\u00e8 1 (v\u00d7 1 < 2 ). 17 17 17 17 194. HD : V\u00edi 1 < x < 10 th\u00d7 x l\u00b5 c\u00b8c s\u00e8 8 v\u00b5 9 (v\u00d7 1 < 8 < 10 v\u00b5 1 < 9 < 10 ). 7 7 7 7 7 7 195. a) 1 + 1 = 1+1 = 2 =1 b) 3 + 1 = 3 +1 = 4 = 1 2 2 2 2 8 8 8 8 2 101","c) 7 + 5 = 7 + 5 = 12 = 4 d) 1 + 2 = 1+ 2 = 3 = 1 9 9 9 9 3 6 6 6 6 2 e) 3 + 7 = 3 + 7 = 10 = 5 g) 2 + 3 = 2 + 3 = 5 =1 8 8 8 8 4 5 5 5 5 196. a) 1 + 2 = 3 + 8 = 11 b) 2 + 2 = 6 + 14 = 20 4 3 12 12 12 7 3 21 21 21 c) 2 + 1 = 8 + 5 = 13 d) 1 + 1 = 3 + 2 = 5 5 4 20 20 20 2 3 6 6 6 e) 1 + 3 = 5 + 9 = 14 g) 4 + 1 = 8 + 5 = 13 3 5 15 15 15 5 2 10 10 10 197. a) 1 + 1 = 2 + 1 = 3 b) 2 + 1 = 4 + 1 = 5 2 4 4 4 4 3 6 6 6 6 c) 7 + 1 = 7 + 6 = 13 d) 1 + 3 = 1 + 6 = 7 12 2 12 12 12 8 4 8 8 8 e) 2 + 1 = 8 + 1 = 9 = 3 g) 5 + 5 = 15 + 5 = 20 = 5 3 12 12 12 12 4 8 24 24 24 24 6 198. a) 1 + 5 = 3 + 10 = 13 b) 2 + 1 = 4 + 3 = 7 4 6 12 12 12 9 6 18 18 18 c) 1 + 3 = 4 + 9 = 13 d) 3 + 5 = 12 + 25 = 37 6 8 24 24 24 10 8 40 40 40 e) 7 + 1 = 14 + 3 = 17 g) 3 + 7 = 15 + 28 = 43 12 8 24 24 24 20 25 100 100 100 199. a) 3 + 1 = 15 + 4 = 19 b) 1 + 5 = 1 + 15 = 16 = 4 4 5 20 20 20 36 12 36 36 36 9 c) 3 + 1 = 9 + 2 = 11 d) 1 + 7 = 5 + 28 = 33 4 6 12 12 12 8 10 40 40 40 e) 1 + 5 = 3 + 20 = 23 g) 2 + 2 = 14 + 6 = 20 8 6 24 24 24 3 7 21 21 21 200. a) 2 + 5 = 1 + 5 = 13 b) 1 + 12 = 1 + 3 = 7 8 6 4 6 12 8 16 8 4 8 c) 1 + 6 = 1 + 1 = 9 d) 12 + 12 = 2 + 2 = 20 4 30 4 5 20 18 42 3 7 21 102","201. a) 1 + 2 + 3 = 1+ 2+ 3 = 6 7 7 7 7 7 b) 1 + 3 + 7 = 1+ 3 + 7 = 11 20 20 20 20 20 c) 2 + 4 + 4 = 2 +4+ 4 = 10 = 2 15 15 15 15 15 3 d) 1 + 7 + 4 = 1+ 7+ 4 = 12 = 4 9 9 9 9 9 3 202. a) 1 + 1 + 1 = 6 + 3 + 1 = 10 = 5 3 6 18 18 18 18 18 9 b) 1 + 1 + 2 = 1 + 5 + 8 = 14 = 7 20 4 5 20 20 20 20 10 c) 1 + 1 + 3 = 1 + 2 + 9 = 12 =1 12 6 4 12 12 12 12 d) 1 + 2 + 3 = 25 + 8 + 3 = 36 = 9 4 25 100 100 100 100 100 25 203. a) 3 + 4 + 4 + 5 = \uf8eb 3 + 4 \uf8f6 + \uf8eb 4 + 5 \uf8f6 = 1+1=2 7 9 7 9 \uf8ed\uf8ec 7 7 \uf8f8\uf8f7 \uf8ed\uf8ec 9 9 \uf8f8\uf8f7 b) 1 + 4 + 4 + 7 = \uf8eb 1 + 4 \uf8f6 + \uf8eb 4 + 171\uf8f6\uf8f8\uf8f7 =1+ 1=2 5 11 5 11 \uf8ed\uf8ec 5 5 \uf8f8\uf8f7 \uf8ed\uf8ec 11 c) 1 + 4 + 5 + 7 = \uf8eb 1 + 4 \uf8f6 + \uf8eb 5 + 7 \uf8f6 = 5 + 12 15 15 18 18 \uf8ed\uf8ec 15 15 \uf8f8\uf8f7 \uf8ec\uf8ed 18 18 \uf8f7\uf8f8 15 18 = 1 + 2 = 1 3 3 d) 1 + 1 + 3 + 5 = \uf8eb 1 + 3 \uf8f6 + \uf8eb 1 + 5 \uf8f6 = 4 + 6 = 1 + 1 = 1 8 12 8 12 \uf8ec\uf8ed 8 8 \uf8f7\uf8f8 \uf8ec\uf8ed 12 12 \uf8f8\uf8f7 8 12 2 2 204. a) 5 + 4 = 1 b) 2 + 1 =1 c) 1 + 3 = 1 9 9 3 3 4 4 d) 9 + 2 = 1 e) 7 + 5 = 1 g) 2 + 3 =1 11 11 12 12 5 5 103","205. HD : V\u00d7 4 + 2 = 22 , m\u00b5 4 + 2 = 66 n\u00aan 22 = 66 . Ta c\u00e3 22 = 66 . 5 3 15 5 3 15 15 45 V\u00cby s\u00e8 th\u00ddch h\u00eep vi\u00d5t v\u00b5o \u00ab tr\u00e8ng l\u00b5 s\u00e8 45. 206. HD : C\u00b6 hai ng\u00b5y \u00ab t\u00ab \u00aei \u00ae\u2212\u00eec l\u00b5 : 1 + 1 = 3 (qu\u00b7ng \u00ae\u2212\u00eang) 4 2 4 207. HD : C\u00b8ch 1 : 2 + 1 = 4 + 1 = 5 3 6 6 6 6 Th\u00eai gian m\u00e9t ti\u00d5t h\u00e4c v\u00b5 gi\u00ea ngh\u00d8 k\u00d0o d\u00b5i trong 5 gi\u00ea. 6 C\u00b8ch 2 : 2 gi\u00ea = 60 ph\u00f3t \u00d7 2 = 40 ph\u00f3t 3 3 1 gi\u00ea = 60 ph\u00f3t \u00d7 1 = 10 ph\u00f3t 6 6 40 + 10 = 50 (ph\u00f3t) Th\u00eai gian m\u00e9t ti\u00d5t h\u00e4c v\u00b5 gi\u00ea ngh\u00d8 k\u00d0o d\u00b5i trong 50 ph\u00f3t. 208. HD : H\u00e9p th\u00f8 hai \u00ae\u00f9ng \u00ae\u2212\u00eec l\u00b5 : 1 + 1 = 9 (kg) 4 5 20 C\u00b6 hai h\u00e9p \u00ae\u00f9ng \u00ae\u2212\u00eec l\u00b5 : 1 + 9 = 7 (kg) 4 20 10 209. a) 15 \u2212 3 = 15 \u2212 3 = 12 = 3 b) 17 \u2212 7 = 17 \u2212 7 = 10 = 1 16 16 16 16 4 20 20 20 20 2 c) 19 \u2212 4 = 19 \u2212 4 = 15 = 5 d) 37 \u2212 13 = 37 \u2212 13 = 24 = 3 21 21 21 21 7 40 40 40 40 5 e) 57 \u2212 17 = 57 \u2212 17 = 40 = 2 100 100 100 100 5 g) 7 \u2212 1 = 7 \u22121 = 6 = 1 12 12 12 12 2 104","210. a) 1 \u2212 1 = 4 \u2212 1 = 3 b) 17 \u2212 5 = 17 \u2212 15 = 2 = 1 2 8 8 8 8 18 6 18 18 18 9 c) 2 \u2212 4 = 6 \u2212 4 = 2 d) 2 \u2212 1 = 4 \u2212 1 = 3 = 1 3 9 9 9 9 3 6 6 6 6 2 e) 7 \u2212 1 = 7 \u2212 2 = 5 = 1 g) 8 \u2212 2 = 8 \u2212 6 = 2 10 5 10 10 10 2 15 5 15 15 15 211. a) 1 \u2212 2 = 5 \u2212 4 = 1 b) 2 \u2212 3 = 16 \u2212 9 = 7 2 5 10 10 10 3 8 24 24 24 c) 5 \u2212 3 = 10 \u2212 9 = 1 d) 7 \u2212 5 = 21 \u2212 10 = 11 6 4 12 12 12 8 12 24 24 24 e) 5 \u2212 3 = 25 \u2212 9 = 16 = 8 g) 9 \u2212 5 = 27 \u2212 25 = 2 = 1 6 10 30 30 30 15 10 6 30 30 30 15 212. a) 1 \u2212 1 = 4 \u2212 3 = 1 b) 1 \u2212 1 = 5 \u2212 4 = 1 3 4 12 12 12 4 5 20 20 20 c) 7 \u2212 1 = 28 \u2212 9 = 19 d) 6 \u2212 3 = 60 \u2212 21 = 39 9 4 36 36 36 7 10 70 70 70 e) 5 \u2212 1 = 20 \u2212 9 = 11 g) 5 \u2212 2 = 25 \u2212 16 = 9 9 4 36 36 36 8 5 40 40 40 213. a) 1 \u2212 1 = 2 \u2212 1 = 1 b) 1 \u2212 3 = 10 \u2212 3 = 7 2 2 2 2 10 10 10 10 c) 3 \u2212 1 = 9 \u2212 1 = 8 d) 4 \u2212 1 = 36 \u2212 1 = 35 3 3 3 3 9 9 9 9 e) 8 \u2212 2 = 24 \u2212 2 = 22 g) 5 \u2212 2 = 25 \u2212 2 = 23 3 3 3 3 5 5 5 5 214. a) 5 \u2212 2 = 1 \u2212 2 = 15 \u2212 4 = 11 10 15 2 15 30 30 30 b) 5 \u2212 1 = 1 \u2212 1 = 3 \u2212 2 = 1 20 6 4 6 12 12 12 c) 6 \u2212 6 = 1 \u2212 1 = 4 \u2212 3 = 1 18 24 3 4 12 12 12 d) 5 \u2212 3 = 5 \u2212 1 = 20 \u2212 9 = 11 9 12 9 4 36 36 36 105","215. HD : a) x = 5 \u2212 1 = 5 \u2212 3 = 2 = 1 ; b) x = 3 \u2212 1 = 2 = 1 6 2 6 6 6 3 4 4 4 2 c) x = 3 + 1 = 3 + 2 = 5 = 1 ; d) x = 5 \u2212 1 = 5 \u2212 2 = 3 = 1 10 5 10 10 10 2 6 3 6 6 6 2 e) x = 1 \u2212 3 = 5 \u2212 3 = 2 = 1 ; g) x = 3 \u2212 1 = 3 \u2212 2 = 1 2 10 10 10 10 5 8 4 8 8 8 216. C\u00b8c ph\u00a9n s\u00e8 vi\u00d5t v\u00b5o \u00ab tr\u00e8ng \u00eb c\u00b8c h\u00b5ng l\u00b5 : a) 7 ; 3 ; 1 b) 5 ; 2 ; 7 . 686 14 9 10 217. a) 7 \u2212 \uf8eb 5 \u2212 2 \uf8f6 = 7 \u2212 \uf8eb 25 \u2212 16 \uf8f6 = 7 \u2212 9 = 14 \u2212 9 = 5 = 1 20 \uf8ec\uf8ed 8 5 \uf8f8\uf8f7 20 \uf8ed\uf8ec 40 40 \uf8f8\uf8f7 20 40 40 40 40 8 b) 5 + \uf8eb 5 \u2212 1 \uf8f6 = 5 + \uf8eb 20 \u2212 9 \uf8f6 = 5 + 11 = 30 + 11 = 41 6 \uf8ed\uf8ec 9 4 \uf8f8\uf8f7 6 \uf8ed\uf8ec 36 36 \uf8f8\uf8f7 6 36 36 36 36 c) 9 \u2212 \uf8eb 2 + 3 \uf8f6 + 7 = 9 \u2212 \uf8eb 4 + 3 \uf8f6 + 7 10 \uf8ed\uf8ec 5 10 \uf8f8\uf8f7 20 10 \uf8ec\uf8ed 10 10 \uf8f8\uf8f7 20 = 9 \u2212 7 + 7 = 2 + 7 = 4 + 7 = 11 10 10 20 10 20 20 20 20 218. a) Ta c\u00e3 : 1 > 1 n\u00aan 1 + 1 >1+ 1 3 5 3 5 b) Ta c\u00e3 : 1 < 1 n\u00aan 1 \u2212 1 > 1\u2212 1 7 4 7 4 c) Ta c\u00e3 : 19 > 17 n\u00aan 1+ 19 > 1+ 17 30 30 30 30 d) Ta c\u00e3 : 20 > 18 n\u00aan 1 \u2212 20 < 1\u2212 18 . 23 23 23 23 219. HD : H\u00e9p b\u00b8nh c\u00dfn l\u00b9i c\u00a9n n\u00c6ng l\u00b5 : 4 \u2212 1 = 11 (kg) 5 4 20 106","220. HD : Ng\u00b5y th\u00f8 hai m\u00b8y c\u00b5y \u00ae\u2212\u00eec nhi\u00d2u h\u00acn ng\u00b5y \u00ae\u00c7u v\u00b5 nhi\u00d2u h\u00acn l\u00b5 : 2 \u2212 3 = 1 (c\u00b8nh \u00ae\u00e5ng) 5 8 40 221. HD : S\u00e8 g\u00b9o c\u00dfn l\u00b9i l\u00b5 : 3 \u2212 1 = 1 (t\u00can) 5 2 10 1 t\u00can = 1 t\u00b9. 10 222. a) 1 \u00d7 2 = 2 b) 1 \u00d7 5 = 5 c) 3 \u00d7 1 = 3 3 7 21 2 6 12 4 4 16 d) 3 \u00d7 1 = 3 e) 4 \u00d7 2 = 8 g) 2 \u00d7 7 = 14 5 2 10 9 3 27 3 5 15 223. a) 4 \u00d7 5 = 4\u00d75 = 4 b) 8 \u00d7 3 = 24 = 8 5 7 5\u00d77 7 9 5 45 15 c) 5 \u00d7 4 = 20 = 10 d) 3 \u00d7 2 = 3\u00d72 = 2 6 7 42 21 7 3 7\u00d73 7 e) 7 \u00d7 4 = 7\u00d74 = 4 g) 7 \u00d7 3 = 21 = 7 5 7 5\u00d77 5 9 5 45 15 224. a) 3 \u00d7 2 = 6 = 1 4 9 36 6 b) 12 \u00d7 13 = 12 \u00d7 13 = 12 = 4 13 15 13 \u00d7 15 15 5 c) 8 \u00d7 7 = 8\u00d77 = 4\u00d72\u00d77 = 4 21 10 21 \u00d7 10 7\u00d73\u00d72\u00d75 15 d) 7 \u00d7 15 = 7 \u00d7 15 = 7\u00d75\u00d73 = 3 5 14 5 \u00d7 14 5\u00d72\u00d77 2 e) 8 \u00d7 25 = 8 \u00d7 25 = 2\u00d74\u00d75\u00d75 = 10 15 28 15 \u00d7 28 3\u00d75\u00d74\u00d77 21 g) 2 \u00d7 5 = 2\u00d75 = 2\u00d75 = 1 15 22 15 \u00d7 22 3 \u00d7 5 \u00d7 2 \u00d7 11 33 107","225. a) 3 \u00d7 1 = 3 b) 1 \u00d7 2 = 2 = 1 8 2 16 4 9 36 18 c) 3 \u00d7 1 = 3 = 1 d) 1 \u00d7 2 = 2 5 6 30 10 3 5 15 e) 3 \u00d7 1 = 3 g) 5 \u00d7 1 = 5 = 1 8 4 32 6 5 30 6 226. a) 2 \u00d7 3 = 6 b) 7 \u00d7 2 = 14 7 7 9 9 c) 2 \u00d7 15 = 30 = 6 d) 3 \u00d7 1 = 3 = 1 5 5 6 6 2 e) 5 \u00d7 3 = 15 g) 9 \u00d7 5 = 45 = 15 13 13 6 6 2 227. a) 1 \u00d7 2 \u00d7 3 = 1\u00d7 2 \u00d7 3 = 1 2 3 4 2\u00d73\u00d74 4 b) 7 \u00d7 8 \u00d7 9 = 7\u00d78\u00d79 = 7 8 9 10 8 \u00d7 9 \u00d7 10 10 c) 5 \u00d7 7 \u00d7 28 = 5 \u00d7 7 \u00d7 28 = 5 \u00d7 7 \u00d7 14 \u00d7 2 = 2 14 15 7 14 \u00d7 15 \u00d7 7 14 \u00d7 5 \u00d7 3 \u00d7 7 3 d) 2 \u00d7 1 \u00d73\u00d7 1 \u00d74\u00d7 1 \u00d75\u00d7 1 = 2 3 4 5 = \uf8ed\uf8eb\uf8ec 2 \u00d7 1 \uf8f8\uf8f6\uf8f7 \u00d7 \uf8eb\uf8ed\uf8ec 3 \u00d7 1 \uf8f8\uf8f6\uf8f7 \u00d7 \uf8ed\uf8eb\uf8ec 4 \u00d7 1 \uf8f6\uf8f8\uf8f7 \u00d7 \uf8eb\uf8ec\uf8ed 5 \u00d7 1 \uf8f6\uf8f8\uf8f7 = 1 2 3 4 5 228. a) 2 \u00d7 10 \u00d7 3 = \uf8eb2 \u00d7 3 \uf8f6 \u00d7 10 = 10 3 21 2 \uf8ec\uf8ed 3 2 \uf8f8\uf8f7 21 21 b) 22 \u00d7 12 \u00d7 5 = \uf8ec\uf8ed\uf8eb 22 \u00d7 5 \uf8f7\uf8f6\uf8f8 \u00d7 12 = 12 5 22 5 22 c) 7 \u00d7 23 \u00d7 2 = \uf8eb 7 \u00d7 2 \uf8f6 \u00d7 23 = 23 2 81 7 \uf8ed\uf8ec 2 7 \uf8f7\uf8f8 81 81 d) 5 \u00d7 21 \u00d7 47 \u00d7 0= \uf8eb5 \u00d7 21 47 \uf8f6 \u00d7 0 = 0. 17 4 15 \uf8ec\uf8ed 17 4\u00d7 15 \uf8f8\uf8f7 108","229. a) \uf8eb 1 + 3 \uf8f6 \u00d7 4 = 1 \u00d74 + 3 \u00d7 4 =2+3=5 \uf8ed\uf8ec 2 4 \uf8f8\uf8f7 2 4 b) \uf8eb 5 \u2212 1 \uf8f6 \u00d7 7 = 5 \u00d7 7\u2212 1 \u00d77=5\u2212 1 = 9 \uf8ec\uf8ed 7 14 \uf8f8\uf8f7 7 14 2 2 c) 1 \u00d7 3 + 1 \u00d7 1 = 1 \u00d7 \uf8ec\uf8eb\uf8ed 3 + 1 \uf8f6\uf8f7\uf8f8 = 1 \u00d71 = 1 2 4 2 4 2 4 4 2 2 d) 11 \u00d7 26 \u2212 26 \u00d7 8 = 26 \u00d7 \uf8eb 11 \u2212 8 \uf8f6 = 26 \u00d71 = 26 3 7 7 3 7 \uf8ec\uf8ed 3 3 \uf8f8\uf8f7 7 7 230. HD : Ta c\u00e3 : 3 + 2 \u00d72 \u2212 2 = 3 + 4 \u2212 2 = 1 5 5 5 5 5 5 M\u00b5 : 3 \u00d7 ... = 1. V\u00cby ph\u00a9n s\u00e8 th\u00ddch h\u00eep vi\u00d5t v\u00b5o ch\u00e7 ch\u00cam l\u00b5 5 . 5 3 231. HD : S\u00e8 m\u00d0t d\u00a9y l\u00f4a c\u00ab Lan c\u00c7n d\u00efng l\u00b5 : 5 \u00d74 = 10 (m) 6 3 232. HD : C\u00b8ch t\u00ddnh th\u00eai gian c\u00f1a 5 ti\u00d5t h\u00e4c nh\u2212 sau : C\u00b8ch 1 : 2 \u00d7 5 = 10 (gi\u00ea) 3 3 1 gi\u00ea = 60 ph\u00f3t v\u00b5 60 \u00d7 10 = 200 3 V\u00cby 10 gi\u00ea = 200 ph\u00f3t. 3 C\u00b8ch 2 : 2 gi\u00ea = 40 ph\u00f3t 3 40 \u00d7 5 = 200 (ph\u00f3t) 233. HD : Di\u00d6n t\u00ddch c\u00a8n ph\u00dfng l\u00b5 : 11 \u00d7 7 = 77 (m2) 2 2 4 109","234. HD : Sau 1 gi\u00ea ng\u2212\u00eai \u00ae\u00e3 \u00aei \u00ae\u2212\u00eec l\u00b5 : 3 12 \u00d7 1 = 4 (km) 3 235. HD : S\u00e8 b\u00b9n nam l\u00b5 : 24 \u00d7 3 = 9 (b\u00b9n) 8 S\u00e8 b\u00b9n c\u00f1a \u00ae\u00e9i v\u00a8n ngh\u00d6 l\u00b5 : 24 + 9 = 33 (b\u00b9n) 236. a) 2 \u00d7 3 \u00d7 4 = 2 ; b) 1\u00d7 2 \u00d7 3 \u00d7 4 = 1\u00d7 2 \u00d7 3 \u00d7 4 = 1 3 \u00d7 4 \u00d7 5 5 5\u00d76\u00d77\u00d78 5\u00d72\u00d73\u00d77\u00d72\u00d74 70 c) 5 \u00d7 6 \u00d7 7 = 5\u00d76\u00d77 = 5 ; d) 2 \u00d7 3 \u00d7 5 = 2\u00d73\u00d75 = 6 = 1 6 7 8 6\u00d77\u00d78 8 5 4 6 5\u00d74\u00d76 24 4 237. 5 ; 9 ; 5 ; 4 ; 3 ; 8 . 2 7 12 9 1 1 238. a) 2 : 5 = 2 \u00d7 7 = 14 b) 1 : 1 = 1 \u00d7 2 = 2 = 1 3 7 3 5 15 4 2 4 1 4 2 c) 2 : 2 = 2 \u00d7 3 = 2 \u00d7 3 = 3 d) 3 : 1 = 3 \u00d7 2 = 6 = 3 5 3 5 2 5 \u00d7 2 5 4 2 4 1 4 2 e) 3 : 3 = 3 \u00d7 5 = 3\u00d75 = 5 g) 4 : 8 = 4 \u00d7 9 = 4\u00d79 = 4 = 1 7 5 7 3 7\u00d73 7 9 9 9 8 9\u00d78 8 2 239. a) 2 : 1 = 2\u00d77 = 14 b) 4 : 2 = 6 7 1 3 c) 3 : 3 = 5 d) 3 : 1 =6 5 2 e) 5: 9 = 50 g) 10 : 7 = 100 10 9 10 7 240. a) 1 : 1 = 3 b) 1 : 1 = 4 c) 1 : 3 = 4 3 4 4 3 d) 1 : 2 = 7 e) 1 : 5 = 6 g) 1 : 2 = 3 72 6 5 3 2 110","241. a) 4 : 2 = 2 b) 3 : 2 = 3 c) 10 : 5 = 2 99 5 10 21 21 d) 6 : 3 = 2 e) 5 : 3 = 5 g) 2 : 4 = 1 7 7 7 21 3 6 242. a) x = 1 : 1 = 1 b) x = 6 : 2 = 3 63 2 55 c) x = 3 : 2 = 3 d) x = 1 : 5 = 1 2 5 25 e) x = 4 : 6 = 4 = 2 g) x = 1 : 3 = 1 6 3 3 9 243. C\u00b8c ph\u00a9n s\u00e8 vi\u00d5t v\u00b5o \u00ab tr\u00e8ng \u00eb c\u00b8c h\u00b5ng l\u00b5 : a) 9 ; 3 ; 8 b) 15 ; 7 ; 1 16 5 7 8 52 244. a) 3 \u00d7 8 =1 b) 5 \u00d7 4 =1 c) 5 \u00d7 2 =1 8 3 4 5 2 5 d) 3 \u00d7 4 =1 e) 1 \u00d7 9 =1 g) 12 \u00d7 1 = 1 4 3 9 1 12 245. HD : Chi\u00d2u r\u00e9ng h\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 : 5 : 7 = 5 (m) 8 8 7 Chu vi h\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 : \uf8eb 7 + 5 \uf8f6 \u00d7 2 = 89 (m) \uf8ec\uf8ed 8 7 \uf8f7\uf8f8 28 246. HD : C\u00b8ch 1 : S\u00e8 l\u00ddt s\u00f7a H\u00b5 u\u00e8ng h\u00d5t trong m\u00e9t tu\u00c7n l\u00b5 : 1 \u00d77= 7 (l) 4 4 S\u00e8 chai s\u00f7a H\u00b5 \u00ae\u00b7 u\u00e8ng trong m\u00e9t tu\u00c7n l\u00b5 : 7 : 7 = 3 (chai) 4 12 111","C\u00b8ch 2 : S\u00e8 ph\u00c7n chai s\u00f7a H\u00b5 u\u00e8ng trong m\u00e9t ng\u00b5y l\u00b5 : 1 : 7 = 3 (chai) 4 12 7 S\u00e8 chai s\u00f7a H\u00b5 u\u00e8ng trong m\u00e9t tu\u00c7n l\u00b5 : 3 \u00d7 7 = 3 (chai) 7 247. a) 2 \u00d7 1 : 1 = 1 : 1 = 3 b) 2 : 2 \u00d7 1 = 1 \u00d7 1 = 1 5 2 3 5 3 5 9 3 2 3 2 6 c) 1 \u00d7 1 + 1 = 1 + 1 = 5 d) 2 : 2 \u2212 1 = 3 \u2212 1 = 2 . 2 3 4 6 4 12 7 3 7 7 7 7 248. a) S ; b) S ; c) S ; d) \u00a7. 249. a) H\u00d7nh thoi l\u00b5 c\u00b8c h\u00d7nh : (3) v\u00b5 (6) b) H\u00d7nh b\u00d7nh h\u00b5nh l\u00b5 c\u00b8c h\u00d7nh : (2) v\u00b5 (5) c) H\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 c\u00b8c h\u00d7nh : (4) v\u00b5 (7) d) H\u00d7nh vu\u00abng l\u00b5 c\u00b8c h\u00d7nh : (1) v\u00b5 (8) 250. v\u00b5 251. H\u00e4c sinh t\u00f9 v\u00cf. 252. C\u00b8c s\u00e8 \u00aeo di\u00d6n t\u00ddch vi\u00d5t v\u00b5o \u00ab tr\u00e8ng l\u00c7n l\u2212\u00eet l\u00b5 : 1 cm2 ; 4 m2 ; 2dm2. 4 25 253. HD : \u00a7\u00e9 d\u00b5i \u00ae\u2212\u00eang ch\u00d0o th\u00f8 hai l\u00b5 : (4 \u00d7 2) : 3 = 40 (dm) 5 3 254. HD : Di\u00d6n t\u00ddch khu \u00ae\u00cat l\u00b5 : (70 \u00d7 300) : 2 = 10500 (m2) 255. Khoanh v\u00b5o D. 112","Ch\u2212\u00acng n\u00a8m T\u00d8 s\u00e8 - m\u00e9t s\u00e8 b\u00b5i to\u00b8n li\u00aan quan \u00ae\u00d5n t\u00d8 s\u00e8. t\u00d8 l\u00d6 b\u00b6n \u00ae\u00e5 256. \u00a7S : a) 5 b) 7 . 7 5 257. \u00a7S : a) 3 b) 4 c) 8 d) 6 (= 23 ). 5 7 5 9 258. HD : S\u00e8 b\u00b9n c\u00f1a c\u00b6 \u00ae\u00e9i v\u00a8n ngh\u00d6 l\u00b5 : 4 + 5 = 9 (b\u00b9n) a) T\u00d8 s\u00e8 c\u00f1a s\u00e8 b\u00b9n trai v\u00b5 t\u00e6ng s\u00e8 b\u00b9n c\u00f1a c\u00b6 \u00ae\u00e9i l\u00b5 : 4 . 9 b) T\u00d8 s\u00e8 c\u00f1a s\u00e8 b\u00b9n g\u00b8i v\u00b5 t\u00e6ng s\u00e8 b\u00b9n c\u00f1a c\u00b6 \u00ae\u00e9i l\u00b5 : 5 . 9 259. B\u00b5i gi\u00b6i Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 2 + 5 = 7 (ph\u00c7n) S\u00e8 b\u00d0 l\u00b5 : 84 : 7 \u00d7 2 = 24 S\u00e8 l\u00edn l\u00b5 : 84 \u2212 24 = 60 \u00a7\u00b8p s\u00e8 : S\u00e8 b\u00d0 : 24 ; S\u00e8 l\u00edn : 60. 260. HD : 113","Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 1 + 4 = 5 (ph\u00c7n) S\u00e8 tr\u00a9u \u00eb tr\u00aan b\u00b7i c\u00e1 l\u00b5 : 25 : 5 = 5 (con) S\u00e8 b\u00df \u00eb tr\u00aan b\u00b7i c\u00e1 l\u00b5 : 25 \u2212 5 = 20 (con) 261. HD : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 + 3 = 8 (ph\u00c7n) An mua quy\u00d3n truy\u00d6n \u00ae\u00e3 h\u00d5t s\u00e8 ti\u00d2n l\u00b5 : 16000 : 8 \u00d7 5 = 10000 (\u00ae\u00e5ng) 262. HD : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 3 + 1 = 4 (ph\u00c7n) S\u00e8 l\u00ddt s\u00acn \u00ae\u00e1 d\u00efng \u00ae\u00d3 pha l\u00b5 : 28 : 4 \u00d7 3 = 21 (l) 263. HD : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 + 7 = 12 (ph\u00c7n) 114","S\u00e8 tem D\u00f2ng s\u2212u t\u00c7m \u00ae\u2212\u00eec l\u00b5 : 180 : 12 \u00d7 5 = 75 (c\u00b8i tem) 264. Ch\u00bcng h\u00b9n : L\u00edp 4A v\u00b5 l\u00edp 4B c\u00e3 t\u00cat c\u00b6 55 h\u00e4c sinh. T\u00ddnh s\u00e8 h\u00e4c sinh c\u00f1a m\u00e7i l\u00edp, bi\u00d5t r\u00bbng s\u00e8 h\u00e4c sinh c\u00f1a l\u00edp 4A b\u00bbng 5 s\u00e8 h\u00e4c sinh c\u00f1a l\u00edp 4B. 6 B\u00b5i gi\u00b6i Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 + 6 = 11 (ph\u00c7n) S\u00e8 h\u00e4c sinh c\u00f1a l\u00edp 4A l\u00b5 : 55 : 11 \u00d7 5 = 25 (h\u00e4c sinh) S\u00e8 h\u00e4c sinh c\u00f1a l\u00edp 4B l\u00b5 : 55 \u2212 25 = 30 (h\u00e4c sinh) \u00a7\u00b8p s\u00e8 : L\u00edp 4A : 25 h\u00e4c sinh ; L\u00edp 4B : 30 h\u00e4c sinh. 265. B\u00b5i gi\u00b6i V\u00d7 s\u00e8 th\u00f8 nh\u00cat gi\u00b6m 7 l\u00c7n th\u00d7 \u00ae\u2212\u00eec s\u00e8 th\u00f8 hai n\u00aan s\u00e8 th\u00f8 nh\u00cat g\u00cap 7 l\u00c7n s\u00e8 th\u00f8 hai. Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 7 + 1 = 8 (ph\u00c7n) 115","S\u00e8 th\u00f8 hai l\u00b5 : 96 : 8 = 12 S\u00e8 th\u00f8 nh\u00cat l\u00b5 : 96 \u2212 12 = 84 \u00a7\u00b8p s\u00e8 : S\u00e8 th\u00f8 nh\u00cat : 84 ; S\u00e8 th\u00f8 hai : 12. 266. HD : N\u00f6a chu vi c\u00f1a s\u00a9n v\u00cbn \u00ae\u00e9ng l\u00b5 : 400 : 2 = 200 (m) Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 2 + 3 = 5 (ph\u00c7n) Chi\u00d2u r\u00e9ng c\u00f1a s\u00a9n v\u00cbn \u00ae\u00e9ng l\u00b5 : 200 : 5 \u00d7 2 = 80 (m) Chi\u00d2u d\u00b5i c\u00f1a s\u00a9n v\u00cbn \u00ae\u00e9ng l\u00b5 : 200 \u2212 80 = 120 (m) 267. HD : S\u00e8 v\u00b6i c\u00b6 hai ng\u00b5y c\u00f6a h\u00b5ng \u00ae\u00e3 b\u00b8n \u00ae\u2212\u00eec l\u00b5 : 35 \u00d7 2 = 70 (m) Ta c\u00e3 s\u00ac \u00ae\u00e5 : 116","Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 3 + 4 = 7 (ph\u00c7n) Ng\u00b5y th\u00f8 nh\u00cat c\u00f6a h\u00b5ng \u00ae\u00e3 b\u00b8n \u00ae\u2212\u00eec s\u00e8 v\u00b6i l\u00b5 : 70 : 7 \u00d7 3 = 30 (m) Ng\u00b5y th\u00f8 hai c\u00f6a h\u00b5ng \u00ae\u00e3 b\u00b8n \u00ae\u2212\u00eec s\u00e8 v\u00b6i l\u00b5 : 70 \u2212 30 = 40 (m) 268. HD : Vi\u00d5t th\u00aam ch\u00f7 s\u00e8 0 v\u00b5o b\u00aan ph\u00b6i s\u00e8 th\u00f8 nh\u00cat th\u00d7 \u00ae\u2212\u00eec s\u00e8 th\u00f8 hai n\u00aan s\u00e8 th\u00f8 hai g\u00cap 10 l\u00c7n s\u00e8 th\u00f8 nh\u00cat. Bi\u00d3u th\u00de s\u00e8 th\u00f8 nh\u00cat l\u00b5 1 ph\u00c7n th\u00d7 s\u00e8 th\u00f8 hai l\u00b5 10 ph\u00c7n nh\u2212 th\u00d5. T\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 1 + 10 = 11 (ph\u00c7n) S\u00e8 th\u00f8 nh\u00cat l\u00b5 : 231 : 11 = 21 S\u00e8 th\u00f8 hai l\u00b5 : 231 \u2212 21 = 210 269. B\u00b5i gi\u00b6i Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 8 \u2212 5 = 3 (ph\u00c7n) S\u00e8 b\u00d0 l\u00b5 : 36 : 3 \u00d7 5 = 60 S\u00e8 l\u00edn l\u00b5 : 60 + 36 = 96 \u00a7\u00b8p s\u00e8 : S\u00e8 b\u00d0 : 60 ; S\u00e8 l\u00edn : 96. 117","270. HD : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 \u2212 3 = 2 (ph\u00c7n) Tu\u00e6i ch\u00de n\u00a8m nay l\u00b5 : 8 : 2 \u00d7 5 = 20 (tu\u00e6i) 271. HD : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 \u2212 1 = 4 (ph\u00c7n) S\u00e8 g\u00b9o n\u00d5p l\u00b5 : 480 : 4 = 120 (kg) S\u00e8 g\u00b9o t\u00ce l\u00b5 : 120 + 480 = 600 (kg) 272. HD : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 \u2212 3 = 2 (ph\u00c7n) Chi\u00d2u cao c\u00f1a b\u00e8 l\u00b5 : 68 : 2 \u00d7 5 = 170 (cm) 118","273. HD : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 7 \u2212 5 = 2 (ph\u00c7n) S\u00e8 h\u00e4c sinh g\u00b8i l\u00b5 : 120 : 2 \u00d7 5 = 300 (h\u00e4c sinh) S\u00e8 h\u00e4c sinh trai l\u00b5 : 300 + 120 = 420 (h\u00e4c sinh). 274. Ch\u00bcng h\u00b9n : Hu\u00d6 c\u00e3 nhi\u00d2u h\u00acn Lan 16 quy\u00d3n v\u00eb. T\u00d7m s\u00e8 v\u00eb c\u00f1a m\u00e7i b\u00b9n, bi\u00d5t r\u00bbng s\u00e8 v\u00eb c\u00f1a Lan b\u00bbng 1 s\u00e8 v\u00eb c\u00f1a Hu\u00d6. 3 B\u00b5i gi\u00b6i Ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 3 \u2212 1 = 2 (ph\u00c7n) S\u00e8 v\u00eb c\u00f1a Lan l\u00b5 : 16 : 2 = 8 (quy\u00d3n) S\u00e8 v\u00eb c\u00f1a Hu\u00d6 l\u00b5 : 8 + 16 = 24 (quy\u00d3n) \u00a7\u00b8p s\u00e8 : Lan : 8 quy\u00d3n v\u00eb ; Hu\u00d6 : 24 quy\u00d3n v\u00eb. 119","275. HD : Chi\u00d2u r\u00e9ng m\u00b6nh v\u2212\u00ean l\u00b5 : 15 \u00d7 3 = 45 (m) Chi\u00d2u d\u00b5i m\u00b6nh v\u2212\u00ean l\u00b5 : 15 \u00d7 4 = 60 (m) Di\u00d6n t\u00ddch m\u00b6nh v\u2212\u00ean \u00ae\u00e3 l\u00b5 : 60 \u00d7 45 = 2700 (m2) 276. HD : S\u00e8 l\u00edn nh\u00cat c\u00e3 hai ch\u00f7 s\u00e8 l\u00b5 99 n\u00aan hi\u00d6u c\u00f1a hai s\u00e8 \u00ae\u00e3 l\u00b5 99. Bi\u00d3u th\u00de s\u00e8 b\u00d0 l\u00b5 9 ph\u00c7n b\u00bbng nhau th\u00d7 s\u00e8 l\u00edn l\u00b5 20 ph\u00c7n nh\u2212 th\u00d5. Hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : S\u00e8 b\u00d0 l\u00b5 : 20 \u2212 9 = 11 (ph\u00c7n) S\u00e8 l\u00edn l\u00b5 : 99 : 11 \u00d7 9 = 81 81 + 99 = 180 277. HD : Sau 3 n\u00a8m n\u00f7a m\u00d1 v\u00c9n h\u00acn con 28 tu\u00e6i, ta c\u00e3 s\u00ac \u00ae\u00e5 : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 5 \u2212 1 = 4 (ph\u00c7n) Tu\u00e6i con sau 3 n\u00a8m n\u00f7a l\u00b5 : 28 : 4 = 7 (tu\u00e6i) Tu\u00e6i con hi\u00d6n nay l\u00b5 : 7 \u2212 3 = 4 (tu\u00e6i) 120","Tu\u00e6i m\u00d1 hi\u00d6n nay l\u00b5 : 4 + 28 = 32 (tu\u00e6i) 278. HD : Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 7 \u2212 2 = 5 (ph\u00c7n) Tu\u00e6i b\u00e8 n\u00a8m nay l\u00b5 : 30 : 5 \u00d7 7 = 42 (tu\u00e6i) 279. T\u00d8 l\u00d6 b\u00b6n \u00ae\u00e5 1 : 800 1 : 1000 1 : 10 000 1 : 2000 \u00a7\u00e9 d\u00b5i thu nh\u00e1 5dm 7cm 4cm 25mm 4000dm 50 000mm \u00a7\u00e9 d\u00b5i th\u00cbt 7000cm 40 000cm 280. B\u00b5i gi\u00b6i Qu\u00b7ng \u00ae\u2212\u00eang H\u00b5 N\u00e9i \u2212 L\u00b9ng S\u00acn d\u00b5i l\u00b5 : 169 \u00d7 1000000 = 169000000 (mm) 169 000 000mm = 169km \u00a7\u00b8p s\u00e8 : 169km. 281. B\u00b5i gi\u00b6i 174km = 174 000 000mm Qu\u00b7ng \u00ae\u2212\u00eang Th\u00b5nh ph\u00e8 H\u00e5 Ch\u00dd Minh \u2212 C\u00c7n Th\u00ac tr\u00aan b\u00b6n \u00ae\u00e5 d\u00b5i l\u00b5 : 174000000 : 1000000 = 174 (mm) \u00a7\u00b8p s\u00e8 : 174mm. 282. Khoanh v\u00b5o C. 121","Ch\u2212\u00acng s\u00b8u \u00abn t\u00cbp cu\u00e8i n\u00a8m 283. a) 572 618 ; 572 619 ; 572 620 ; 572 621 ; 572 622. b) 46 859 300 ; 46 859 301 ; 46 859 302 ; 46 859 303 ; 46 859 304. c) 28 634 997 ; 28 634 998 ; 28 634 999 ; 28 635 000 ; 28 635 001. (HS \u00ae\u00e4c s\u00e8 nh\u2212 c\u00b8ch \u00ae\u00e4c trong SGK) 284. a) 5 280 670 ; 5 280 671 ; 5 280 672. b) 70 800 994 ; 70 800 995 ; 70 800 996. c) 99 999 998 ; 99 999 999 ; 100 000 000. \u00a7\u00e4c s\u00e8 : ch\u00bcng h\u00b9n 70 800 996 \u00ae\u00e4c l\u00b5 : b\u00b6y m\u2212\u00aci tri\u00d6u t\u00b8m tr\u00a8m ngh\u00d7n ch\u00ddn tr\u00a8m ch\u00ddn m\u2212\u00aci s\u00b8u. 285. a) 0 ; 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 ; 8. b) 6870 ; 6872 ; 6874 ; 6876 ; 6878. c) 986 713 ; 986 715 ; 986 717 ; 986 719 ; 986 721. d) 720 ; 730 ; 740 ; 750 ; 760. e) 60 000 000 ; 70 000 000 ; 80 000 000 ; 90 000 000. \u00a7\u00e4c s\u00e8 : t\u2212\u00acng t\u00f9 nh\u2212 b\u00b5i 284. 286. a) 0 ; 1 ; 2 ; 3 ; 4 ; 5 ; ... b) 0 ; 2 ; 4 ; 6 ; 8 ; 10 ; 12 ; ... c) 1 ; 3 ; 5 ; 7 ; 9 ; 11 ; 13 ; ... Ch\u00f3 \u00fd : Khi \u00ae\u00e4c m\u00e7i d\u00b7y s\u00e8 tr\u00aan, HS ph\u00b6i \u00ae\u00e4c d\u00cau \\\"...\\\" l\u00b5 \\\"v\u00a9n v\u00a9n\\\" \u00ae\u00d3 ch\u00d8 d\u00b7y s\u00e8 c\u00dfn k\u00d0o d\u00b5i m\u00b7i. 287. a) \u00a7 ; b) S ; c) S ; d) \u00a7 ; e) \u00a7 ; g) \u00a7 ; h) \u00a7. 288. a) 20 000 ; b) 20 ; c) 2 000 000 ; d) 200 000 000 ; e) 20 t\u00d8 (t\u00f8c l\u00b5 20 000 000 000). 289. S\u00e8 l\u00edn nh\u00cat l\u00b5 987 643. V\u00cby khoanh v\u00b5o C. 122","290. S\u00e8 b\u00d0 nh\u00cat l\u00b5 5 050 505. V\u00cby khoanh v\u00b5o A. 291. a) 425 496 < 425 596 ; b) 791 325 > 791 235 c) 80808 + 1212 = 82020 d) 989898 \u00d7 3 < 989898 \u00d7 5 (Hai t\u00ddch c\u00e3 th\u00f5a s\u00e8 th\u00f8 nh\u00cat b\u00bbng nhau v\u00b5 kh\u00b8c 0, t\u00ddch n\u00b5o c\u00e3 th\u00f5a s\u00e8 th\u00f8 hai l\u00edn h\u00acn th\u00d7 t\u00ddch \u00ae\u00e3 l\u00edn h\u00acn). e) 5555 \u00d7 4 + 5555 = 5555 \u00d7 5 (v\u00d7 5555 \u00d7 4 + 5555 = 5555 \u00d7 (4 + 1) = 5555 \u00d7 5). 292. a) C\u00b8c s\u00e8 253 967 ; 235 967 ; 253 679 ; 235 976 vi\u00d5t theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 \u00ae\u00d5n l\u00edn l\u00b5 : 235 967 ; 235 976 ; 253 679 ; 253 967. V\u00cby khoanh v\u00b5o C. b) 11 001 ; 10 110 ; 10 101 ; 10 011. 293. a) 68257 b) 95832 c) 1954 + 17629 \u2212 47106 \u00d7 253 85886 48726 5862 9770 3908 494362 d) 130050 425 e) 1942 g) 19183 78 02550 306 \u00d7 204 358 245 000 7768 463 3884 73 396168 19183 : 78 = 245 (d\u2212 73) h) 4278 00 9500 i) 1099 478 45 \u00d7 03 500 549500 427800 : 9500 = 45 (d\u2212 300) 294. a) 9900 : 36 \u2212 15 \u00d7 11 = 275 \u2212 165 = 110 123","b) 1036 + 64 \u00d7 52 \u2212 1827 = 1036 + 3328 \u2212 1827 = 4364 \u2212 1827 = 2537 c) (15792 : 336) \u00d7 5 + 27 \u00d7 11 = 47 \u00d7 5 + 27 \u00d7 11 = 235 + 297 = 532 295. a 150 567 655 1500 10223 5204 b 120 317 305 600 15427 5019 a + b 270 884 960 2100 a\u2212b 30 250 350 900 296. a) m + n = n + m ; a\u00d7b=b\u00d7a b) a + 0 = 0 + a = a ; a\u00d71=1\u00d7a=a c) (a + b) + c = a + (b + c) ; (a \u00d7 b) \u00d7 c = a \u00d7 (b \u00d7 c) d) 35 \u00d7 99 + 65 \u00d7 99 = (35 + 65) \u00d7 99 = 100 \u00d7 99 = 9900 e) (84 + 16) \u00d7 75 = 84 \u00d7 75 + 16 \u00d7 75 = 6300 + 1200 = 7500 297. a) 25 + 69 + 75 + 11 = (25 + 75) + (69 + 11) = 100 + 80 = 180 b) 25 \u00d7 989 \u00d7 4 + 25 = (25 \u00d7 4) \u00d7 989 + 25 = 100 \u00d7 989 + 25 = 98900 + 25 = 98925 c) 64 \u00d7 867 + 36 \u00d7 867 = (64 + 36) \u00d7 867 = 100 \u00d7 867 = 86700 d) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = (1 + 10) + (2 + 9) + (3 + 8) + (4 + 7) + (5 + 6) = 11 + 11 + 11 + 11 + 11 = 11 \u00d7 5 = 55 124","Nh\u00cbn x\u00d0t : T\u00e6ng c\u00f1a c\u00b8c s\u00e8 t\u00f9 nhi\u00aan t\u00f5 1 \u00ae\u00d5n 10 c\u00e3 10 s\u00e8 h\u00b9ng, c\u00e9ng t\u00f5ng c\u00c6p hai s\u00e8 h\u00b9ng nh\u2212 tr\u00aan ta c\u00e3 5 c\u00c6p, m\u00e7i c\u00c6p c\u00e3 t\u00e6ng b\u00bbng 11 n\u00aan t\u00e6ng c\u00c7n t\u00d7m l\u00b5 11 \u00d7 5 = 55. 298. HD : D\u00f9a v\u00b5o nh\u00cbn x\u00d0t \u00eb ph\u00c7n d) c\u00f1a b\u00b5i 297 ta c\u00e3 th\u00d3 n\u00aau nh\u00cbn x\u00d0t sau \u00ae\u00e8i v\u00edi b\u00b5i 298 : \u2022 C\u00b8c s\u00e8 t\u00f9 nhi\u00aan li\u00aan ti\u00d5p t\u00f5 1 \u00ae\u00d5n 100 c\u00e3 100 s\u00e8, do \u00ae\u00e3 c\u00e3 100 : 2 = 50 c\u00c6p g\u00e5m hai s\u00e8 h\u00b9ng. \u2022 M\u00e7i c\u00c6p hai s\u00e8 h\u00b9ng \u00ae\u00d2u c\u00e3 t\u00e6ng b\u00bbng nhau v\u00b5 b\u00bbng 101 : (1 + 100) + (2 + 99) + (3 + 98) + ... + (50 + 51) \u2022 V\u00cby t\u00e6ng c\u00f1a c\u00b8c s\u00e8 t\u00f9 nhi\u00aan li\u00aan ti\u00d5p t\u00f5 1 \u00ae\u00d5n 100 l\u00b5 : 1 + 2 + 3 + 4 + 5 + ... + 96 + 97 + 98 + 99 + 100 = 101 \u00d7 50 = 5050 299. a) x + 121 = 300 b) x \u2212 354 = 246 x = 300 \u2212 121 x = 246 + 354 x = 179 x = 600 c) 800 \u2212 x = 490 d) x \u00d7 36 = 540 x = 800 \u2212 490 x = 540 : 36 x = 310 x = 15 e) x : 53 = 60 g) 2040 : x = 85 x = 60 \u00d7 53 x = 2040 : 85 x = 3180 x = 24 300. a) C\u00b8c s\u00e8 9732 ; 4530 chia h\u00d5t cho 2. C\u00b8c s\u00e8 9732 ; 4530 ; 8361 ; 807 chia h\u00d5t cho 3. b) C\u00b8c s\u00e8 815 ; 4530 chia h\u00d5t cho 5. S\u00e8 8361 chia h\u00d5t cho 9. c) C\u00b8c s\u00e8 9732 ; 4530 v\u00f5a chia h\u00d5t cho 2 v\u00f5a chia h\u00d5t cho 3. d) S\u00e8 4530 v\u00f5a chia h\u00d5t cho 2 v\u00f5a chia h\u00d5t cho 5. e) S\u00e8 8361 v\u00f5a chia h\u00d5t cho 3 v\u00f5a chia h\u00d5t cho 9. 125","301. a) 2 34 ; 5 34 ; 8 34 ; b) 75 0 ; c) 2 4 3 ; d) 8 3 1 ; 8 6 1 ; e) 8 0 1 ; 8 9 1. 302. HD : a) x ph\u00b6i l\u00b5 s\u00e8 tr\u00dfn ch\u00f4c v\u00b5 350 < x < 390, n\u00aan x l\u00b5 c\u00b8c s\u00e8 : 360 ; 370 ; 380. b) T\u2212\u00acng t\u00f9 nh\u2212 tr\u00aan, x l\u00b5 c\u00b8c s\u00e8 : 1950 ; 1960. 303. a) C\u00e3 4 h\u00e4c sinh cao 148cm. b) C\u00e3 9 h\u00e4c sinh cao 150cm. c) C\u00e3 6 h\u00e4c sinh cao 151cm v\u00b5 c\u00e3 8 h\u00e4c sinh cao 152cm, n\u00aan c\u00e3 6 + 8 = 14 (h\u00e4c sinh) cao h\u00acn 150cm. d) C\u00e3 8 h\u00e4c sinh c\u00efng cao nh\u00cat l\u00edp, m\u00e7i h\u00e4c sinh \u00ae\u00e3 \u00ae\u00d2u c\u00e3 chi\u00d2u cao l\u00b5 152cm. 304. a) 1 (m\u00e9t ph\u00c7n n\u00a8m) ; b) 3 (ba ph\u00c7n t\u00b8m) ; 5 8 c) 2 (hai ph\u00c7n ba) ; d) 7 (b\u00b6y ph\u00c7n m\u2212\u00eai). 3 10 305. a) B\u00e8n ph\u00c7n ch\u00ddn ; hai ph\u00c7n ch\u00ddn ; b\u00b6y ph\u00c7n ch\u00ddn. b) T\u00b8m ph\u00c7n m\u2212\u00eai m\u00e9t ; t\u00b8m ph\u00c7n m\u2212\u00eai l\u00a8m ; t\u00b8m ph\u00c7n m\u2212\u00eai ch\u00ddn. 306. Ph\u00a9n s\u00e8 16 b\u00bbng 4 . 20 5 307. Ch\u00bcng h\u00b9n : a) 16 ; 24 ; 32 ; b) 12 ; 15 ; 18 . 30 45 60 16 20 24 c) C\u00e3 th\u00d3 gi\u00b6i nh\u2212 sau : \u2212 Ta c\u00e3 : 75 = 75 : 5 = 15 = 15 :3 = 5 . 120 120 : 5 24 24 :3 8 126","V\u00cby ph\u00a9n s\u00e8 5 b\u00bbng 75 v\u00b5 c\u00e3 m\u00c9u s\u00e8 b\u00d0 nh\u00cat (v\u00d7 l\u00b5 ph\u00a9n s\u00e8 t\u00e8i gi\u00b6n). 8 120 \u2212 Ho\u00c6c n\u00aau nh\u00cbn x\u00d0t, ch\u00bcng h\u00b9n : Ph\u00a9n s\u00e8 b\u00bbng 75 m\u00b5 c\u00e3 m\u00c9u s\u00e8 120 b\u00d0 nh\u00cat ph\u00b6i l\u00b5 ph\u00a9n s\u00e8 t\u00e8i gi\u00b6n sau khi r\u00f3t g\u00e4n 75 , do \u00ae\u00e3 : 120 75 = 75 : 15 = 5 . Ph\u00a9n s\u00e8 c\u00c7n t\u00d7m l\u00b5 5 . 120 120 : 15 8 8 308. a) 11 < 13 ; 15 15 b) Quy \u00ae\u00e5ng m\u00c9u s\u00e8 c\u00f1a 3 v\u00b5 5 \u00ae\u2212\u00eec 27 v\u00b5 20 , m\u00b5 27 > 20 , 4 9 36 36 36 36 v\u00cby 3 > 5 . 4 9 c) T\u2212\u00acng t\u00f9 nh\u2212 ph\u00c7n b) \u00ae\u00d3 c\u00e3 8 < 8 ; ho\u00c6c : hai ph\u00a9n s\u00e8 8 v\u00b5 8 11 9 11 9 c\u00e3 c\u00efng t\u00f6 s\u00e8, ph\u00a9n s\u00e8 n\u00b5o c\u00e3 m\u00c9u s\u00e8 l\u00edn h\u00acn th\u00d7 ph\u00a9n s\u00e8 \u00ae\u00e3 b\u00d0 h\u00acn n\u00aan 8 < 8 . 11 9 d) T\u2212\u00acng t\u00f9 nh\u2212 ph\u00c7n b), ch\u00e4n m\u00c9u s\u00e8 chung l\u00b5 60 \u00ae\u00d3 c\u00e3 40 v\u00b5 50 , 60 60 m\u00b5 40 < 50 n\u00aan 8 < 25 ; ho\u00c6c c\u00e3 th\u00d3 r\u00f3t g\u00e4n 8 v\u00b5 25 \u00ae\u00d3 c\u00e3 2 60 60 12 30 12 30 3 v\u00b5 5 r\u00e5i ch\u00e4n 6 l\u00b5 m\u00c9u s\u00e8 chung \u00ae\u00d3 quy \u00ae\u00e5ng m\u00c9u s\u00e8 \u00ae\u2212\u00eec 4 < 5 , 6 6 6 do \u00ae\u00e3 8 < 25 . 12 30 e) T\u2212\u00acng t\u00f9 nh\u2212 ph\u00c7n d) r\u00f3t g\u00e4n ph\u00a9n s\u00e8 16 \u00ae\u2212\u00eec 4 . \u00a7\u00d3 so s\u00b8nh 4 36 9 9 v\u00b5 14 , ch\u00e4n m\u00c9u s\u00e8 chung l\u00b5 27 r\u00e5i quy \u00ae\u00e5ng m\u00c9u s\u00e8 \u00ae\u2212\u00eec 12 v\u00b5 27 27 14 , m\u00b5 12 < 14 , v\u00cby 16 < 14 . 27 27 27 36 27 309. Ch\u00bcng h\u00b9n : a) 9 ; b) 2 ; c) 15 . 8 5 15 127","310. a) Ta c\u00e3 : 7 = 14 ; 11 < 14 ; 14 < 14 ; n\u00aan c\u00b8c ph\u00a9n s\u00e8 11 ; 14 ; 7 9 18 18 18 18 15 18 15 9 vi\u00d5t theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 \u00ae\u00d5n l\u00edn l\u00b5 : 11 ; 7 ; 14 . 18 9 15 b) V\u00d7 8 < 1 c\u00dfn 9 > 1 ; 15 > 1 n\u00aan ch\u00d8 c\u00c7n so s\u00b8nh 9 v\u00b5 15 ; quy 9 5 11 5 11 \u00ae\u00e5ng m\u00c9u s\u00e8 \u00ae\u2212\u00eec 99 v\u00b5 75 ; m\u00b5 75 < 99 . V\u00cby c\u00b8c ph\u00a9n s\u00e8 9 ; 55 55 55 55 5 8 ; 15 vi\u00d5t theo th\u00f8 t\u00f9 t\u00f5 b\u00d0 \u00ae\u00d5n l\u00edn l\u00b5 : 8 ; 15 ; 9 . 9 11 9 11 5 311. \u00a7S : a) 55 ; 25 ; 19 . b) 11 ; 1 ; 1 . 63 24 27 24 10 4 c) 9 ; 5 ; 5 . d) 2 ; 2 . 5 7 16 3 312. a) 2\u00d73\u00d78 = 2\u00d7 3 \u00d7 2 \u00d7 4 = 2 . 4\u00d75\u00d76\u00d77 4 \u00d75\u00d7 3 \u00d7 2 \u00d77 35 b) 36 \u00d7 22 \u00d7 51 = 36 \u00d7 11 \u00d7 2 \u00d7 17 \u00d7 3 = 3. 11 \u00d7 17 \u00d7 72 11 \u00d7 17 \u00d7 36 \u00d7 2 313. a) 3 t\u00b9 = 30 y\u00d5n 2 y\u00d5n 8kg = 28kg 40 y\u00d5n = 4 t\u00b9 5 t\u00b9 35kg = 535kg 5 t\u00can = 50 t\u00b9 8000kg = 8 t\u00can 120 t\u00b9 = 12 t\u00can 4 t\u00can 45kg = 4045kg b) 3 gi\u00ea = 180 ph\u00f3t 3 gi\u00ea 45 ph\u00f3t = 225 ph\u00f3t 360 gi\u00a9y = 6 ph\u00f3t 1 gi\u00ea = 15 ph\u00f3t 4 10 th\u00d5 k\u00d8 = 1000 n\u00a8m c) 800cm2 = 8dm2 6000 n\u00a8m = 60 th\u00d5 k\u00d8 1200dm2 = 12m2 7m2 68dm2 = 768dm2 2 000 000m2 = 2km2 80 000cm2 = 8m2 4km2 400m2 = 4 000 400m2 128","314. a) 3 t\u00can > 25 t\u00b9 5 t\u00can 45kg = 5045kg b) 1 gi\u00ea < 45 ph\u00f3t 3 ph\u00f3t > 30 gi\u00a9y 2 4 c) 50m2 40dm2 > 5004dm2 100cm2 = 1 m2 100 315. a) P = a \u00d7 4 b) P = (a + b) \u00d7 2 S=a\u00d7a S=a\u00d7b c) S = a \u00d7 h d) S = m\u00d7 n 2 316. HD : a) C\u00e3 th\u00d3 n\u00aau m\u00e9t s\u00e8 \u00ae\u00c6c \u00aei\u00d3m ch\u00f1 y\u00d5u v\u00b5 \u00ae\u00b7 h\u00e4c nh\u2212 sau : \u2212 H\u00d7nh vu\u00abng v\u00b5 h\u00d7nh ch\u00f7 nh\u00cbt : \u2022 \u00a7\u00d2u l\u00b5 h\u00d7nh t\u00f8 gi\u00b8c \u2022 \u00a7\u00d2u c\u00e3 4 g\u00e3c vu\u00abng \u2022 \u00a7\u00d2u c\u00e3 hai c\u00c6p c\u00b9nh \u00ae\u00e8i di\u00d6n song song v\u00b5 t\u00f5ng c\u00c6p c\u00b9nh \u00ae\u00e8i di\u00d6n b\u00bbng nhau \u2022 \u00a7\u00d2u c\u00e3 c\u00b8c c\u00b9nh li\u00aan ti\u00d5p vu\u00abng g\u00e3c v\u00edi nhau. Nh\u00cbn x\u00d0t : H\u00d7nh vu\u00abng \u00ae\u2212\u00eec coi l\u00b5 h\u00d7nh ch\u00f7 nh\u00cbt \u00ae\u00c6c bi\u00d6t c\u00e3 chi\u00d2u d\u00b5i b\u00bbng chi\u00d2u r\u00e9ng. \u2212 H\u00d7nh ch\u00f7 nh\u00cbt v\u00b5 h\u00d7nh b\u00d7nh h\u00b5nh : \u2022 \u00a7\u00d2u l\u00b5 h\u00d7nh t\u00f8 gi\u00b8c \u2022 \u00a7\u00d2u c\u00e3 hai c\u00c6p c\u00b9nh \u00ae\u00e8i di\u00d6n song song v\u00b5 t\u00f5ng c\u00c6p c\u00b9nh \u00ae\u00e8i di\u00d6n b\u00bbng nhau. Nh\u00cbn x\u00d0t : H\u00d7nh ch\u00f7 nh\u00cbt \u00ae\u2212\u00eec coi l\u00b5 h\u00d7nh b\u00d7nh h\u00b5nh \u00ae\u00c6c bi\u00d6t c\u00e3 4 g\u00e3c vu\u00abng. \u2212 H\u00d7nh thoi v\u00b5 h\u00d7nh vu\u00abng : \u2022 \u00a7\u00d2u l\u00b5 h\u00d7nh t\u00f8 gi\u00b8c \u2022 \u00a7\u00d2u c\u00e3 c\u00b8c c\u00c6p c\u00b9nh \u00ae\u00e8i di\u00d6n song song v\u00b5 b\u00bbng nhau. Nh\u00cbn x\u00d0t : H\u00d7nh vu\u00abng \u00ae\u2212\u00eec coi l\u00b5 h\u00d7nh thoi \u00ae\u00c6c bi\u00d6t c\u00e3 4 g\u00e3c vu\u00abng. 129","b) C\u00e3 th\u00d3 n\u00aau nh\u2212 sau : \u2212 H\u00d7nh vu\u00abng v\u00b5 h\u00d7nh ch\u00f7 nh\u00cbt kh\u00b8c nhau \u00eb ch\u00e7 h\u00d7nh vu\u00abng c\u00e3 4 c\u00b9nh b\u00bbng nhau, h\u00d7nh ch\u00f7 nh\u00cbt ch\u00d8 c\u00e3 hai chi\u00d2u d\u00b5i b\u00bbng nhau v\u00b5 hai chi\u00d2u r\u00e9ng b\u00bbng nhau. \u2212 H\u00d7nh ch\u00f7 nh\u00cbt kh\u00b8c h\u00d7nh b\u00d7nh h\u00b5nh \u00eb ch\u00e7 : H\u00d7nh ch\u00f7 nh\u00cbt c\u00e3 4 g\u00e3c vu\u00abng. \u2212 H\u00d7nh thoi kh\u00b8c h\u00d7nh vu\u00abng \u00eb ch\u00e7 : H\u00d7nh thoi (n\u00e3i chung) kh\u00abng c\u00e3 c\u00b8c g\u00e3c vu\u00abng. 317. B\u00b5i gi\u00b6i a) Chu vi h\u00d7nh vu\u00abng l\u00b5 : 4 \u00d7 4 = 16 (cm) Di\u00d6n t\u00ddch h\u00d7nh vu\u00abng l\u00b5 : 4 \u00d7 4 = 16 (cm2) \u00a7\u00b8p s\u00e8 : 16cm ; 16cm2. b) Chi\u00d2u r\u00e9ng c\u00f1a h\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 : 6\u00d7 2 = 4 (cm) 3 Chu vi h\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 : (6 + 4) \u00d7 2 = 20 (cm) Di\u00d6n t\u00ddch h\u00d7nh ch\u00f7 nh\u00cbt l\u00b5 : 6 \u00d7 4 = 24 (cm2) \u00a7\u00b8p s\u00e8 : 20cm ; 24cm2. c) Chi\u00d2u cao c\u00f1a h\u00d7nh b\u00d7nh h\u00b5nh l\u00b5 : 18 \u00d7 5 = 10 (cm) 9 Di\u00d6n t\u00ddch h\u00d7nh b\u00d7nh h\u00b5nh l\u00b5 : 18 \u00d7 10 = 180 (cm2) \u00a7\u00b8p s\u00e8 : 180cm2. 130","d) \u00a7\u00e9 d\u00b5i \u00ae\u2212\u00eang ch\u00d0o BD l\u00b5 : 20 \u00d7 3 = 12 (cm) 5 Di\u00d6n t\u00ddch h\u00d7nh thoi ABCD l\u00b5 : (20 \u00d7 12) : 2 = 120 (cm2) \u00a7\u00b8p s\u00e8 : 120cm2. 318. Di\u00d6n t\u00ddch c\u00f1a ph\u00c7n t\u00ab \u00ae\u00cbm trong h\u00d7nh v\u00cf l\u00b5 22cm2. V\u00cby khoanh v\u00b5o C. Ch\u00f3 \u00fd : Tr\u00aan h\u00d7nh v\u00cf, di\u00d6n t\u00ddch ph\u00c7n t\u00ab \u00ae\u00cbm l\u00b5 hi\u00d6u di\u00d6n t\u00ddch c\u00f1a hai h\u00d7nh ch\u00f7 nh\u00cbt : h\u00d7nh ch\u00f7 nh\u00cbt c\u00e3 chi\u00d2u d\u00b5i 7cm, chi\u00d2u r\u00e9ng 6cm, di\u00d6n t\u00ddch l\u00b5 7 \u00d7 6 = 42 (cm2) v\u00b5 h\u00d7nh ch\u00f7 nh\u00cbt c\u00e3 chi\u00d2u d\u00b5i l\u00b5 : 7 \u2212 1 \u2212 1 = 5 (cm), chi\u00d2u r\u00e9ng l\u00b5 : 6 \u2212 1 \u2212 1 = 4 (cm), di\u00d6n t\u00ddch l\u00b5 : 5 \u00d7 4 = 20 (cm2). Nh\u2212 v\u00cby, di\u00d6n t\u00ddch ph\u00c7n t\u00ab \u00ae\u00cbm l\u00b5 : 42 \u2212 20 = 22 (cm2). 319. Chu vi c\u00f1a h\u00d7nh \u00ae\u00b7 cho l\u00b5 20cm. V\u00cby khoanh v\u00b5o B. Ch\u00f3 \u00fd : C\u00e3 th\u00d3 gi\u00b6i th\u00ddch b\u00bbng c\u00b8c c\u00b8ch kh\u00b8c nhau, ch\u00bcng h\u00b9n, c\u00e3 th\u00d3 coi h\u00d7nh b\u00aan l\u00b5 do m\u00e9t h\u00d7nh ch\u00f7 nh\u00cbt c\u00e3 chi\u00d2u d\u00b5i 7cm, chi\u00d2u r\u00e9ng 3cm c\u00bet \u00aei m\u00e9t h\u00d7nh ch\u00f7 nh\u00cbt \u00eb g\u00e3c ph\u00b6i. Nh\u2212 th\u00d5, chu vi c\u00f1a h\u00d7nh \u00ae\u00b7 cho tr\u2212\u00edc b\u00bbng chu vi c\u00f1a h\u00d7nh ch\u00f7 nh\u00cbt c\u00e3 chi\u00d2u d\u00b5i 7cm, chi\u00d2u r\u00e9ng 3cm, do \u00ae\u00e3 chu vi c\u00f1a h\u00d7nh \u00ae\u00b7 cho tr\u2212\u00edc l\u00b5 : (7 + 3) \u00d7 2 = 20 (cm). 320. B\u00b5i gi\u00b6i 15 t\u00b9 = 1500kg a) T\u00e6ng s\u00e8 ng\u00b5y c\u00f6a h\u00b5ng b\u00b8n mu\u00e8i l\u00b5 : 4 + 6 = 10 (ng\u00b5y) Trung b\u00d7nh m\u00e7i ng\u00b5y c\u00f6a h\u00b5ng \u00ae\u00b7 b\u00b8n \u00ae\u2212\u00eec l\u00b5 : 1500 : 10 = 150 (kg) 131","b) S\u00e8 ki-l\u00ab-gam mu\u00e8i c\u00f6a h\u00b5ng b\u00b8n \u00ae\u2212\u00eec trong 6 ng\u00b5y sau l\u00b5 : 1500 \u2212 180 = 1320 (kg) Trong 6 ng\u00b5y sau, trung b\u00d7nh m\u00e7i ng\u00b5y c\u00f6a h\u00b5ng \u00ae\u00b7 b\u00b8n \u00ae\u2212\u00eec l\u00b5 : 1320 : 6 = 220 (kg) 220kg = 22 y\u00d5n \u00a7\u00b8p s\u00e8 : a) 150kg mu\u00e8i ; b) 22 y\u00d5n mu\u00e8i. 321. B\u00b5i gi\u00b6i N\u00f6a chu vi c\u00f1a c\u00abng vi\u00aan l\u00b5 : 1280 : 2 = 640 (m) Chi\u00d2u r\u00e9ng c\u00f1a c\u00abng vi\u00aan l\u00b5 : (640 \u2212 160) : 2 = 240 (m) Chi\u00d2u d\u00b5i c\u00f1a c\u00abng vi\u00aan l\u00b5 : 240 + 160 = 400 (m) Di\u00d6n t\u00ddch c\u00f1a c\u00abng vi\u00aan l\u00b5 : 400 \u00d7 240 = 96000 (m2) \u00a7\u00b8p s\u00e8 : 96 000m2. 322. B\u00b5i gi\u00b6i 2 t\u00can = 2000kg Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 3 + 5 = 8 (ph\u00c7n) C\u00f6a h\u00b5ng c\u00e3 s\u00e8 ki-l\u00ab-gam g\u00b9o t\u00ce l\u00b5 : 2000 : 8 \u00d7 5 = 1250 (kg) \u00a7\u00b8p s\u00e8 : 1250kg g\u00b9o t\u00ce. 132","323. B\u00b5i gi\u00b6i Theo s\u00ac \u00ae\u00e5, hi\u00d6u s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 7 \u2212 1 = 6 (ph\u00c7n) Tu\u00e6i con l\u00b5 : 30 : 6 = 5 (tu\u00e6i) Tu\u00e6i m\u00d1 l\u00b5 : 5 \u00d7 7 = 35 (tu\u00e6i) \u00a7\u00b8p s\u00e8 : M\u00d1 : 35 tu\u00e6i ; Con : 5 tu\u00e6i. 324. B\u00b5i gi\u00b6i Theo s\u00ac \u00ae\u00e5, t\u00e6ng s\u00e8 ph\u00c7n b\u00bbng nhau l\u00b5 : 1 + 2 + 6 = 9 (ph\u00c7n) S\u00e8 c\u00a9y h\u00e5ng c\u00e3 trong v\u2212\u00ean l\u00b5 : 540 : 9 = 60 (c\u00a9y) S\u00e8 c\u00a9y na c\u00e3 trong v\u2212\u00ean l\u00b5 : 60 \u00d7 2 = 120 (c\u00a9y) S\u00e8 c\u00a9y b\u2212\u00ebi c\u00e3 trong v\u2212\u00ean l\u00b5 : 120 \u00d7 3 = 360 (c\u00a9y) \u00a7\u00b8p s\u00e8 : 60 c\u00a9y h\u00e5ng ; 120 c\u00a9y na ; 360 c\u00a9y b\u2212\u00ebi. 133","M\u00f4c l\u00f4c Trang C\u00a9u h\u00e1i v\u00b5 H\u2212\u00edng d\u00c9n b\u00b5i t\u00cbp - Tr\u00b6 l\u00eai Ch\u2212\u00acng m\u00e9t : S\u00e8 t\u00f9 nhi\u00aan. B\u00b6ng \u00ae\u00acn v\u00de \u00aeo kh\u00e8i l\u2212\u00eeng 3 60 \u2212 \u00a4n t\u00cbp c\u00b8c s\u00e8 \u00ae\u00d5n 100 000 3 60 \u2212 Bi\u00d3u th\u00f8c c\u00e3 ch\u00f8a m\u00e9t ch\u00f7 5 61 \u2212 C\u00b8c s\u00e8 c\u00e3 s\u00b8u ch\u00f7 s\u00e8 - H\u00b5ng v\u00b5 l\u00edp - So s\u00b8nh c\u00b8c s\u00e8 c\u00e3 nhi\u00d2u ch\u00f7 s\u00e8 - D\u0097y s\u00e8 t\u00f9 nhi\u00aan 5 62 9 65 \u2212 B\u00b6ng \u00ae\u00acn v\u00de \u00aeo kh\u00e8i l\u2212\u00eeng - Gi\u00a9y, th\u00d5 k\u00d8 10 66 \u2212 T\u00d7m s\u00e8 trung b\u00d7nh c\u00e9ng 11 68 \u2212 Bi\u00d3u \u00ae\u00e5 Ch\u2212\u00acng hai : B\u00e8n ph\u00d0p t\u00ddnh v\u00edi c\u00b8c s\u00e8 t\u00f9 nhi\u00aan. H\u00d7nh h\u00e4c 13 69 \u2212 Ph\u00d0p c\u00e9ng v\u00b5 ph\u00d0p tr\u00f5 13 69 \u2212 Bi\u00d3u th\u00f8c c\u00e3 ch\u00f8a hai ch\u00f7, ba ch\u00f7 14 71 \u2212 T\u00d7m hai s\u00e8 khi bi\u00d5t t\u00e6ng v\u00b5 hi\u00d6u c\u00f1a hai s\u00e8 \u00ae\u00e3 15 72 \u2212 G\u00e3c nh\u00e4n, g\u00e3c t\u00ef, g\u00e3c b\u00d1t - Hai \u00ae\u2212\u00eang th\u00bcng vu\u00abng g\u00e3c - Hai \u00ae\u2212\u00eang th\u00bcng song song 16 74 \u2212 Ph\u00d0p nh\u00a9n 17 77 \u2212 Ph\u00d0p chia 21 85 Ch\u2212\u00acng ba : D\u00cau hi\u00d6u chia h\u00d5t cho 2, 5, 9, 3. Gi\u00edi thi\u00d6u 23 90 h\u00d7nh b\u00d7nh h\u00b5nh 23 90 25 91 \u2212 D\u00cau hi\u00d6u chia h\u00d5t cho 2, 5, 9, 3 26 92 \u2212 Ki-l\u00ab-m\u00d0t vu\u00abng \u2212 H\u00d7nh b\u00d7nh h\u00b5nh 134","Ch\u2212\u00acng b\u00e8n : Ph\u00a9n s\u00e8 - C\u00b8c ph\u00d0p t\u00ddnh v\u00edi ph\u00a9n s\u00e8. Trang Gi\u00edi thi\u00d6u h\u00d7nh thoi C\u00a9u h\u00e1i v\u00b5 H\u2212\u00edng d\u00c9n \u2212 Ph\u00a9n s\u00e8 b\u00b5i t\u00cbp - Tr\u00b6 l\u00eai \u2212 Ph\u00a9n s\u00e8 b\u00bbng nhau \u2212 R\u00f3t g\u00e4n ph\u00a9n s\u00e8 29 94 \u2212 Quy \u00ae\u00e5ng m\u00c9u s\u00e8 c\u00b8c ph\u00a9n s\u00e8 29 94 \u2212 So s\u00b8nh c\u00b8c ph\u00a9n s\u00e8 31 96 \u2212 Ph\u00d0p c\u00e9ng ph\u00a9n s\u00e8 33 97 \u2212 Ph\u00d0p tr\u00f5 ph\u00a9n s\u00e8 33 97 \u2212 Ph\u00d0p nh\u00a9n ph\u00a9n s\u00e8 34 99 \u2212 Ph\u00d0p chia ph\u00a9n s\u00e8 36 101 \u2212 H\u00d7nh thoi 38 104 40 107 Ch\u2212\u00acng n\u00a8m : T\u00d8 s\u00e8 - M\u00e9t s\u00e8 b\u00b5i to\u00b8n li\u00aan quan \u00ae\u00d5n t\u00d8 s\u00e8. 42 110 T\u00d8 l\u00d6 b\u00b6n \u00ae\u00e5 44 112 \u2212 T\u00d8 s\u00e8 47 113 \u2212 T\u00d7m hai s\u00e8 khi bi\u00d5t t\u00e6ng v\u00b5 t\u00d8 s\u00e8 c\u00f1a hai s\u00e8 \u00ae\u00e3 47 113 \u2212 T\u00d7m hai s\u00e8 khi bi\u00d5t hi\u00d6u v\u00b5 t\u00d8 s\u00e8 c\u00f1a hai s\u00e8 \u00ae\u00e3 47 113 \u2212 T\u00d8 l\u00d6 b\u00b6n \u00ae\u00e5 v\u00b5 \u00f8ng d\u00f4ng 48 117 49 121 Ch\u2212\u00acng s\u00b8u : \u00a4n t\u00cbp cu\u00e8i n\u00a8m \u2212 S\u00e8 t\u00f9 nhi\u00aan v\u00b5 c\u00b8c ph\u00d0p t\u00ddnh v\u00edi s\u00e8 t\u00f9 nhi\u00aan 51 122 \u2212 Ph\u00a9n s\u00e8 v\u00b5 c\u00b8c ph\u00d0p t\u00ddnh v\u00edi ph\u00a9n s\u00e8 51 122 \u2212 \u00a7\u00b9i l\u2212\u00eeng v\u00b5 \u00aeo \u00ae\u00b9i l\u2212\u00eeng 55 126 \u2212 H\u00d7nh h\u00e4c 57 128 \u2212 Gi\u00b6i b\u00b5i to\u00b8n c\u00e3 l\u00eai v\u00a8n 57 129 59 131 135","Ch\u00deu tr\u00b8ch nhi\u00d6m xu\u00cat b\u00b6n : Ch\u00f1 t\u00dech H\u00e9i \u00ae\u00e5ng Th\u00b5nh vi\u00aan ki\u00aam T\u00e6ng Gi\u00b8m \u00ae\u00e8c Ng\u00ab Tr\u00c7n \u00b8i T\u00e6ng bi\u00aan t\u00cbp ki\u00aam Ph\u00e3 T\u00e6ng Gi\u00b8m \u00ae\u00e8cnguy\u00d4n qu\u00fd thao Bi\u00aan t\u00cbp l\u00c7n \u00ae\u00c7u : nguy\u00d4n th\u00de b\u00d7nh - l\u00aa H\u00e5ng v\u00a9n Bi\u00aan t\u00cbp t\u00b8i b\u00b6n : HO\u00b5NG KIM H\u00b6O Tr\u00d7nh b\u00b5y b\u00d7a : nguy\u00d4n th\u00de h\u00e5ng vy Bi\u00aan t\u00cbp m\u00dc thu\u00cbt : T\u00b5o thanh huy\u00d2n Bi\u00aan t\u00cbp k\u00dc thu\u00cbt : Ho\u00b5ng Anh tu\u00can S\u00f6a b\u00b6n in : V\u00f2 th\u00de \u00b8I nhu Ch\u00d5 b\u00b6n : C\u00abng ty c\u00e6 ph\u00c7n m\u00dc thu\u00cbt v\u00b5 truy\u00d2n th\u00abng b\u00b5i t\u00cbp to\u00b8n 4 M\u00b7 s\u00e8 : 1B419T0 In b\u00b6n, kh\u00e6 17 \u00d7 24 cm. In t\u00b9i S\u00e8 in : S\u00e8 xu\u00cat b\u00b6n : 01-2010\/CXB\/38-1485\/GD In xong v\u00b5 n\u00e9p l\u2212u chi\u00d3u th\u00b8ng n\u00a8m 2010 136"]