Time and Work

Page 1 of 14 LOGITICA Basic To Advanced Bank Math Time and Work Tips and Tricks you must know • Work Done = Time Taken × Rate of Work ������������������������ • Rate of Work = 1 / Time Taken ������������������������������������������������������������ = ������������������������ • Time Taken = 1 / Rate of Work • If a piece of work is done in x number of days, then ������ ������������������������������������������������������������ ∞ ������������������������ the work done in one day = 1/x • Total Wok Done = Number of Days × Efficiency • Efficiency and Time are inversely proportional to each other • If A and B can do a piece of work in X & Y days respectively while working alone, they will together take XY/(X+Y) days to complete it. • If A, B, C can do a piece of work in X, Y, Z days respectively while working alone, they will together take XYZ days to finish it. [XY+YZ+ZX] • X:Y is the ratio of the number of men which are required to complete a piece of work, then the ratio of the time taken by them to complete the work will be Y:X. • If x number of people can do W1 work, in D1 days, working T1 hours each day and the number of people can do W2 work, in D2 days, working T2 hours each day, then the relation between them will be ������1 × ������1 × ������1 = ������1 ������2 × ������2 × ������2 ������2 Type-1: Basic and Simple Unitary Related 1. If 15 men can reap a field in 35 days, in how many days will 21 men reap the same field? St.BL-PO-2008, Ans:25 days 15 men can reap in 35 days Alternative: 1 ,, ,, ,, ,, 15x35 days 15×35 1 21 ,, ,, ,, ,, (15x35)/21 = 25 days 21×d2 = 1 or, d2 = 25 days Similar Math: a. If 6 Workers Can Complete 9 Identical Jobs In 3 Days, How Long Will It Take 4 Workers To Complete 10 Such Jobs? DBBL-MTO-2009, Ans: 5 Days b. If 9 examiners can examine a certain number of answer books in 12 days, working 5 hours a day; for how many hours a day would 4 examiners have to work in order to examine the books in 30 days? BDBL-EO-2014, Ans: 9hrs/day LOGITICA Basic To Advanced Bank Math

Page 2 of 14 LOGITICA Basic To Advanced Bank Math Time and Work ������1 × ������1 × ������1 = ������1 ������2 × ������2 × ������2 ������2 Ref: MCQ-128 MCQ-133 Aggarwal Type-2: Efficient Related 2. A is 30% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 23 days? AD, BB-2016, Aggarwal-49 A’s 100 day’s work ≡ B’s 130 day’s work ⸫ (A+B)’s 1 day’s work = (1/23 + 10/299) So, A’s 23 day’s work ≡ B’s (130*23)/100 = (13+10)/299 ≡ B’s 299/10 day’s work = 1/13 For whole work, they need 13 days Similar math: a. Jaya can make 40 pancakes in a minute. Sally can make pancakes at half of Joya’s rate. What time will it need (in minute) to make 150 cakes, if Shally have already made 30 pancakes alone? [Written exam: NCC Bank-MTO-2018 ] Ans: 3.5 minutes Ref: Ex-9* Ex-10 MCQ-47 MCQ-48 MCQ-52* MCQ-53* Aggarwal [Written Exam: Micro credit-AD- 2021] Written Math: i). Working together, Jose and Jane can complete an assigned task in 20 days. However, if Jose worked alone and complete half the work and then Jane takes over the task and completes the second half of the task, the task will be completed in 45 days. How long will Jose take to complete the task if he worked alone? Assume that Jane is more efficient than Jose. NCC-MTO-2019 Jane takes x days to complete the task Solving equations 1 and 2: alone. Jose takes y days to complete the task (90 - y)y/(90-y + y) = 20 alone. 90y - y^2 = 1800 y^2 - 90y + 1800 = 0 Jane is more efficient than Jose, therefore, (y - 60)(y - 30) = 0 LOGITICA Basic To Advanced Bank Math

Page 3 of 14 LOGITICA Basic To Advanced Bank Math x<y. 1/x + 1/y = 1/20 Time and Work xy/(x+y) = 20 ….eqn 1 x/2 + y/2 = 45 Therefore, y = 30 or 60. Since y > x, x + y = 90 therefore y = 60. x = 90 - y …… eqn 2 Ans: 60 days 3. A takes twice as much time as B or thrice as much time as C to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in: BHBFC Officer-2017, Aggarwal-19 Suppose A, Band C take x, x/2, x/3 days respectively to finish the work. Then, 1/x+2/x+3/x=1/2 ⇒6/x=1/2 ⇒x=12 So, B takes 12/2=6 days to finish the work. Similar math: Ref: Ex-7* Ex-9 MCQ-40 MCQ-45* MCQ-20* MCQ-51* Aggarwal Written Math: i). A teacher has 6 hours to grade all the papers submitted by 35 students in his class. He gets through the first five papers in 1 hour. How much faster should be he work to get the remaining papers in the allotted time? SBL-2018, RBL-2019, Ans: He should be 20% faster. Type-3: Man and Woman Related 4. 4 men and 6 women can complete a work in 8 days, while 3 men and 7 women can complete it in 10 days. In how many days will 10 women complete it? Basic Bank-2018, Aggarwal-12 LOGITICA Basic To Advanced Bank Math

Page 4 of 14 LOGITICA Basic To Advanced Bank Math Time and Work Let 1 man's 1 day's work = x and 1 woman's 1 1 day's work = y. 1 woman's 1 day's work = . 11 400 Then, 4x + 6y = and 3x + 7y = . 10 women's 1 day's work 1x 1 8 10 = 400 10 =. Solving the two equations, we get: 40 x =11/400 and y=1/400 Hence, 10 women will complete the work in 40 days. Similar Math: a. If 3 men or 6 boys can do a piece of work in 10 days, working 7 hours a day; how many days will it take to complete a piece of work twice as large with 6 men and 2 boys working together for 8 hours a day? Pubali Bank-2014, Ans: 7.5 days b. A and B together can do a piece of work in 40 days. A having worked for 20 days, B finishes the remaining work alone in 60 days. In How many days shall B finish the whole work alone? Basic Bank- 2018, Ans: 80 days MCQ-64 MCQ-97 MCQ-98 MCQ-99 MCQ-100 Ref: MCQ-105 MCQ-106 MCQ-109 MCQ-110 MCQ-112 MCQ-115 Aggarwal MCQ-116 MCQ-117 MCQ-118 MCQ-119 MCQ-120 MCQ-121 MCQ-122 MCQ-124 MCQ-126 MCQ-132 Type-4: When people working together and someone left or join 5. A and B together can finish a piece of work in 12 days. If A alone can finish the same work in 20 days, then in how many days will it take B to finish alone? Mercantile Bank Ltd.-2015 A and B one day work= 1/12 Alternative: A alone one day work= 1/20 B alone one day work= (A+B)’s one day’s -A’s one day’s work 12 × 20 = 20 − 12 ������������������������ = 1/12 - 1/20 = 1/30 = 30 ������������������������ As we know that total work is = 1 Then time taken by B to finish the same work =1÷ 1/30 = 1*30/1=30 days LOGITICA Basic To Advanced Bank Math

Page 5 of 14 LOGITICA Similar math: Basic To Advanced Bank Math Time and Work a. A and B together can do a work in 8 days. If A alone can do it in 12 days, then in how many days can B alone do it? RKUB-2017, Ans: 24 days b. A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone? BB-AD-2014, ABL-SO-2017 Son′s 1 day′s work = 1/3 – 1/5 = 15/2. The son alone can do the work in 2/15 =7.5days c. A and B can do a work in 8 days, B and C can do the same work in 12 days. A, B and C together can finish it in 6 days. A and C together will do it in: Probashi Kallyan Bank- 2014 1 3 (A + B + C)'s 1 day's work = ; = 6 24 1 1 (A + B)'s 1 day's work = ; =. 8 8 1 So, A and C together will do the work (B + C)'s 1 day's work = . in 8 days. Ans: 8 days 12 Or……………….. (A + C)'s 1 day's 1 11 (A+B+B+C+C+A)’s one day’s work =2 - + work=1/8+1/12+1/x Or, 2(A+B+C)=(5x+24)/24x 6 8 12 Or, 2*1/6=(5x+24) Or. X=8 (Ans) 15 =- 3 24 Ref: Aggarwal Ex-2 MCQ-12 MCQ-88* Written Math: i). P can complete a work in 12 days working 8 hours a day. Q can complete the same work in 8 days working 10 hours a day. If both P and Q work together, working 8 hours a day, in how many days can they complete the work? JBL-AEO-2020 LOGITICA Basic To Advanced Bank Math

Page 6 of 14 LOGITICA Basic To Advanced Bank Math Time and Work P can complete the work in (P+Q)'s 1 hour's work =(1/96) + (1/80) = (12 x 8) hrs = 96 hrs 11/480. Q can complete the work in So both P and Q will finish the work in (8 x 10) hrs=80 hrs 480/11 hrs Therefore, Number of days of 8 hours each Therefore, P's 1 hour work=1/96 and Q's 1 = (480/11) x (1/8) = 60/11 hour work= 1/80 5 Ans: 511 days ii). Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 15, and 18 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates? SIBL-PO-2014. Ans: 22:15 iii). Abir can do a piece of work in 80 days. He works at it for 10 days and then Bashir alone finishes the remaining work in 42 days. In how many days can the two of them complete the work together? BB-AD-2006, 2017, Abir's 1 days' work = 1/80 ∴ Bashir's 1 days' work =1/48 Aabir's 10 days' work =10/80=1/8 (Abir + Bashir)'s 1 days' work = 1/80 + 1/48 Remaining work =1−81/8=7/8 = (3+5)/240 = 8/240 = 1/30 7/8 of the work is completed by Bashir ∴ Abir and Bashir can complete the whole work in 42 days. together in 30 days ∴ The whole work is completed by Bashir in (42×8)/7 days = 48 days 6. Sam can mow a lawn in 20 minutes and Mark can mow the same lawn in 30 minutes. If they worked together, how long would it take them to do the work? SBL-Sub. Asst. Eng.-201 Alternative: Lawn mowed by Sam in 1 minute =1/20 Lawn mowed by Mark in 1 minute =1/30 20 × 30 ∴ Lawn mowed by both in 1 minute = (1/20+1/30) = 20 + 30 ������������������������������������������ = 12 ������������������������������������������ =5/60 =1/12 Time taken to mow the lawn =12 minutes. Similar math: a. Worker A takes 8 hours to do a job. Worker B takes 10 hours to do the same job. How long should it take worker A and B working to do the same work? JBL-AEO-2015, Ans: ������ ������ ������������������������. [Written exam (value change): JBL, SBL, RBL-2008] ������ LOGITICA Basic To Advanced Bank Math

Page 7 of 14 LOGITICA Basic To Advanced Bank Math Time and Work Ref: Ex-1 MCQ-2 MCQ-3 MCQ-4 MCQ-6 MCQ-10 Aggarwal MCQ-11 MCQ-16 MCQ-54 JBL-AEO 2015 MCQ- MCQ- 130 131 MCQ-17 Written Math: i). A, B and C do a job in 20, 30 and 60 days. In how many days can A do the work if he is assisted by B & C? [Written exam: BB-AD-2013] Ans:10 days 7. A can complete a project in 20 days, and B can complete the same project in 30 days. If A and B start working on the project together and A quits 10 days before the project is completed, in how many days will the project be completed? JBL-EO-20107 Find out how much can they accomplish work in a day A=1/20 and B=1/30 Then suppose x is the number of days required So, A works x-10 days, B works x days In x-10 days A does (x-10)/20 part work and B does x/30 part work. The sum of the works is 1 or whole The equation hence will be_ (x-10)/20+x/30=1 Or, 3x-30+2x=60 Or, x=90/5=18 Answer: 18 days Similar Math: a. A can do a piece of work in 10 days, while B alone can do it in 15 days. They work together for 5 days and the rest of the work is done by C in 2 days. If they get Rs. 450 for the whole work, how should they divide the money? Agrani Bank-2015, Ans: 5/3 days LOGITICA Basic To Advanced Bank Math

Page 8 of 14 LOGITICA Basic To Advanced Bank Math Time and Work When someone join When someone left Ref: Ex-8 Ex-18 MCQ- Ex-14 Ex-16, MCQ-12 Aggarwal 15 19 MCQ-57 MCQ- MCQ- MCQ-56 MCQ-67 62 63 MCQ- MCQ-55 101* [Written Exam: SBL- MCQ- MCQ- 2018, BKB-2011] 103 127 MCQ- 131 MCQ-58 MCQ-65 MCQ-66 MCQ-68 MCQ-69 [Written Exam: BCB- [Written Exam: JO-2008] RBL-SO-2019] MCQ-71 MCQ-72 MCQ-76 MCQ-77, 96 MCQ-78 MCQ-95 [Written Exam: SIBL- 2011, NBL-2017] Written Math: i). Masud can do a job in 40 days, Karim can do the same job in 60 days. They start working together and work for 18 days, when Harun joined them, the three then worked together and finished the job in 5 days. In how many days could Z finish the whole job alone? JBL-AEO- 2011, Ans: 120 days ii). A can do a piece of work in 120 days and B can do it in 150 days. They work together for 20 days then B leaves and A continues the work alone. 12 days after C joins in place of B and the work is completed in 48 days more. In how many days can C do it if he works alone? BSC-Combined exam-2018 L.C.M of 120 & 150 =600 ATQ, Let, Total work =600 unit and efficiency of 20(5+4)+12x5+(5+c)x48=600 C= c. Or, 180+60+240+48c=600 ⸫ Efficiency of A=600/120=5 unit/day Or, 48c=120 Or, c=120/48=2.5 and Efficiency of B=600/150=4 unit/day So, C can complete the work in 600/2.5 days =240 days Ans: 240 days iii). A can reap the field in 15 days, alone. B can reap in 12 days, alone. If A begins alone, and after certain period, B joins him, the field is reaped in 7 1/2 days. How long did A and B work together? PKB-SEO-2018, LOGITICA Basic To Advanced Bank Math

Page 9 of 14 LOGITICA Basic To Advanced Bank Math Time and Work A’s one day’s work =1/15 ⸫A’s 7.5 day’s work=7.5*1/15= ½ ⸫Remaining work =1-1/2=1/2 Now, B can do ½ part in =12*1/2 days = 6 days Ans: 6 days iv). A and B can do some work in 30 days, B and C in 24 days & C and A in 20 days. If they all work for 10 days and B & C leave, how many days more will A take to finish the work? BSC-Combined (Officer-Cash-2018) L.C.M of 30, 24 and 20 =120 unit ATQ. ⸫Efficiency of AB=120/30=4 unit/day 15/2 x10+Px5/2=120 Efficiency of BC=120/24=5 unit/day and Or, 5P/2=120-75 Efficiency of CA=120/20=6 Or, 5P=90 So, Efficiency of ABC=(4+5+6)/2 ⸫P=18 =15/2 unit/day Ans: 18days ⸫A’s efficiency = 15/2-5=5/2 unit/day Let, A take P days more. v). 2 men and 5 women completed 1/4th of a job in 3 days. After that another man joined them and they all complete the next 1/4th of the job in 2 days. How many men can complete the whole job in 4 days? BB-AD-2014, PKSF-2009, Ans: 6 men. Let, (2)-(1)=> 1 man’s one day’s work=x x = 1/8-1/12 = 1/24 1woman’s one day’s work=y So, 1 man can do the work in 24 days. ATQ, ⸫ the work is completed in 24 days by 1 man 3(2x + 5y) =1/4 ⸫ the work is completed in 1 days by 1*24 man 2x + 5y =1/12 ………….(1) ⸫ the work is completed in 24 days by 1*24/4 man 2(3x + 5y) = 1/4 = 6 men 3x + 5y =1/8 …………(2) Ans: 6 men Food for Thought a. A does 80% of a job in 20 days then calls in B and together they finish the remaining work in 3 days. How long does B alone take to do the whole job? Ans: ������������ ������ ������������������������ , Ref: indiabix.com ������ b. A can do a piece of work in 14 days which B can do in 21 days. They begin together but 3 days before the completion of the work. A leaves off. The total number of days to complete the work is? Ans: ������������ ������ ������������������������, Ref: quora.com ������ LOGITICA Basic To Advanced Bank Math

Page 10 of 14 LOGITICA Basic To Advanced Bank Math Time and Work c. P and q need 8 days to complete a work. q and r need 12 days to complete the same work. but p, q and r together can finish it in 6 days. How many days will be needed if p and r together do it? Ans: 8 days, Ref: brainly.com d. A, B and C together can do a piece of work in 40 days. After working with B and C for 16 days, A leaves and then B and C complete the remaining work in 40 days more. A alone could do the work in. Ans: 100 days, Ref: quora.com e. A, B and C can complete a work in 10,12 and 15 days respectively. They started the work together, but A left the work before 5 days of its completion. B also left the work 2 days after A left. In how many days was the work completed. Ans: 7 days, Ref: topper.com Type-5: When working with pair 8. A and B can do some work in 12 days, B and C in 15 days & C and A in 20 days. If A, B and C are together, how many days will it take to complete? PKSF-AM-2014, In 1 day, (A+B) can do 1/12th of the work. On simplification, we get In 1 day, (B+C) can do 1/15th of the work. (A+B+C) = 1/10 In 1 day, (A+C) can do 1/20th of the work. It means that, Now, if we add on the work done by (A+B), In 1 day, (A+B+C) together can do 1/10th of (B+C) and (A+C), we will get the work done the work. by (A+B+C) collectively in 1 day. So, to complete one piece of work together, Therefore, it will take 10 days. (A+B) + (B+C) + (A+C) = 1/12 + 1/15 + 1/20 Ans: 10 days. 2 (A+B+C) = 12/60 Similar Math: a. P does a work in 12 days for 8 hours and Q does in 8 days in 10 hours. If both work for 8 hours, then how many days it needed to complete the work? [Written exam: JBL-AEO-2020], Ans: 5������������������ days Ref: MCQ-33 MCQ-34 MCQ-35 MCQ-36 MCQ-38 MCQ-70 Aggarwal Written Math: i). A and B can do some work in 18 days, B and C in 24 days & C and A in 36 days. How many days will it take to complete If A, B and C are together and separately? BB-AD- 2017, Ans: Together= 16 days and A=48 days, B=144/5 days & C=144 days LOGITICA Basic To Advanced Bank Math

Page 11 of 14 LOGITICA Basic To Advanced Bank Math Time and Work Food for Thought a. A can do a certain work in the same time in which B and C together can do it. If A and B together could do it in 20 days and C alone in 50 days, then B alone could do it in how many days? Ans: 25 days, [Ref. quora.com] Type-6: Working on alternate day (Important written math) 9. A alone can do a piece of work in 30 days, while B alone can do it in 15 days, and C alone can do it in 10 days. If in every second day B, and in every third day C helps A in doing the work, how many days will be required to complete the whole work? Agrani Bank-SO-2017 Efficiency of A, B and C= 1: 2: 3 Remaining= 4 unit total work= 30 unit next 2 days work= 1* 2+ 2* 1= 4 unit First 6 days work= 1* 6+ 2* 3+ 3* 2= 18 Remaining= 0 Remaining Work= 12 unit ⸫Total time= 6+ 3+ 2= 11 days, next 3 days work done by A+ B+ C= 1* 3+ 2* Ans: 11 days 1+ 3* 1= 8 unit. 10. 50 daily workers can complete a dam project in 40 days. If 30 of them work daily and the rest work in every alternative day, how many more days will be required to complete the project? BB-AD-2018, Ans: 10 days 11. Working alone at their respective constant rates, A can complete a task in ‘a’ days and B in ‘b’ days. They take turns in doing the task with each working 2 days at a time. If A starts they finish the task in exactly 10 days. If B starts, they take half a day more. How long does it take to complete the task if they both work together? Aggarwal-94, BSEC (AD)- 2021, Ans: 36/7 days 12. 2 men and 3 boys can do a piece of work in 10 days while 3 men and 2 boys can do the same work in 8 days . In how many days can 2 man and 1 boy do the work? Pubali Bank-2014, JBL-2015, RAKUB-2015 Ans: 12.5 days 13. 16 women take 12 days to complete a work which can be completed by 12 men in 8 days. 16 men started working and after 3 days 10 men left and 4 women joined them. How many days will they take to complete the remaining work ? JBL-AEO(Tellor)-2020, Ans:6 days LOGITICA Basic To Advanced Bank Math

Page 12 of 14 LOGITICA Basic To Advanced Bank Math Time and Work Type-7: Payment depends on efficient/volume of work not working days 14. A can do a piece of work in 12 days while B alone can do it in 15 days. With the help of C they can finish it in 5 days. If they are paid Rs. 960 for the whole work. How much money A gets? A does 1/12 of the work and B does 1/15 of Their efficiency =5:4:3 the work per day. Together they do (LCM of 12, 15 and 20) 1/12+1/15=9/60 or 3/20 of the work. A’s share of wages =5/12 ×960= Rs.400/- C’ s share is 1/5 - 3/20 =1/20 Ans: Rs. 400/- 15. A sum of 3,240 was fixed to complete a work. 54 workers completed the work in 8 days and the sum was divided equally among the workers. If the work was to be completed in 3 days then how much less money each worker would receive compared to when the work was completed in 8 days (sum is divided equally among the workers? Six Bank- PO-2019, Ans: 37.5 taka. 16. A alone can complete a piece of work of Rs.300 in 6 days; but by engaging an assistant, the work is completed in 4 days. Find the share to be received by the assistant. Ans: 100 Rs. Aggarwal-Ex. 3. Food for Thought a. A man and a boy received Rs. 800 as wages for 5 days for the work they did together. The man's efficiency in the work was thrice times that of the boy. What are the daily wages of the boy? Ans: 40 Rs. Ref: examveda.com b. A, B and C can independently do a work in 15 days ,20 days and 30 days, respectively. They work together for some time after which c leaves. A total of Rs. 18000 is paid for the work and B gets 6000 more than C. For how many days did A work? Ans: 8 days, Ref: gmatclub.com L.C.M of 15, 20 & 30 is 60 4:3=12000-2t:6000+t Let, Total work =60 units ⇒24000+4t=36000-6t A:B:C=4:3:2 [efficiency ⇒t=1200 Let, C gets=t So A gets =12000-2400 B gets= 6000+t =9600 A gets=18000-(6000+t+t) So A work LOGITICA Basic To Advanced Bank Math

Page 13 of 14 LOGITICA Basic To Advanced Bank Math Time and Work =12000-2t =(9600*15)/18000 Now, A & B gets money their efficiency. =8 days Type-: Important some advanced Math 17. Two workers A and B are engaged to do a work. A working alone takes 8 hours more to complete the job than if both worked together. If B worked alone, he would need 4.5 hours more to complete the job than they both working together. What time would they take to do the work together? BB-AD-2014 Let A and B together take x hours to complete the work. Then, A alone takes (x + 8) hours And B alone takes (x+9/2) hours to complete the work Then, ⇒1/(x+8) +1/(x+9/2) =1/x ⇒1/(x+8) + 2/(2x+9) = 1/x ⇒x(4x+25) = (x+8)(2x+9) ⇒2x2=72⇒x2=36 ⇒x=6 Ans: 6 hours 18. Nine children can complete a piece of work in 360 days. 18 men can complete the same piece of work in 72 days and 12 women can complete it in 162 days. In how many days can 4 men,12 women and 10 children together complete the piece of work? Aggarwal- Ex. 20. Ans.: 1 man’s 1 day’s work = 1 / (72 x 18) = 1 /1296 One woman’s one day’s work = 1/ (162×12) = 1/1944 1 child’s 1 day’s work = 1/(360×9) = 1/3240 (4 men + 12 women + 10 children)’s one day’s work = (4 x (1/1296)) + (12 x (1/1944)) + (10 x (1/3240) = 1/81 Hence, 4 men, 12 women and 10 children can complete the work in 81 days. LOGITICA Basic To Advanced Bank Math

Page 14 of 14 LOGITICA Basic To Advanced Bank Math Time and Work 19. 10 persons begin to work together on a job but after some days 4 persons leave. As a result, the job which could have been completed in 40 days is completed in 50 days. How many days after the commencement of the work did the 4 persons leave? Aggarwal-Ex. 19. 10 men complete the work in 40 days. So, 1 man complete the same work = 10 *40 = 400 men-days. Work rate of one man = 1/400 Let N = Number of days after start, 4 men leaves. 50 - N = Number of days after 4 men leave. Now, Work rate of one men * total men * number of days = Work completed (1/400) * 10 * N = Part of job completed --------------------------- (1) (1/400) * 6 * (50 -N) =Other Part of job completed --------------------------- (2) Adding (1) and (2) get 1 work completed. (1/400) * 10 * N + (1/400) * 6 * (50 -N) = 1 (1/400) [ 10N - 6N + 300] = 1 4N + 300 = 400 4N = 400 - 300 4N = 100 N = 100/4 = 25 days. Thus, after 25 days 4 men left the work. *Trick: 40 days needed to do the job by 10 persons So, 50 days needed to do the job by 10× 40/50 =8 persons. And as per question remaining person is 10–4=6 So 10 men did 25 days and then remaining 6 men did 25 days. Do all things with love OgMandino The End LOGITICA Basic To Advanced Bank Math