Download - 19289_Time and Work Lecture
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Time And Work
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Work from Days:If A can do a piece of work in n days, then A's 1 day's work =1/n
Days from Work:If A's 1 day's work =1/n ,then A can finish the work in n days
Concept :
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Q. If A can do a piece of work in 10 days and B can complete in 15 days in how many days the work will be completed if they work together.
Let the total work be assumed as LCM(10,15)= 30
Now to complete 30 units A takes 10 daysTo complete 30 units B takes 15 days
Units done in 1 day by A = 3Units done in 1 day by B = 2Units done in 1 day by A & B = 5
To complete 30 units they will take 30/5 = 6days
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Ratio:
If A is thrice as good a workman as B, then:Ratio of work done by A and B = 3 : 1.Ratio of times taken by A and B to finish a work = 1 : 3.
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Examples : (LCM Concepts)Q 1. Worker A takes 8 hours to do a job. Worker B takes 10 hours to do the same job. How long should it take both A and B, working together, to do the same job?
A. 4 2/9 days
B. 4 4/9 days
C. 4 5/9 days
D. 4 7/9 days
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Q2. A and B together can complete a piece of work in 4 days. If A alone can complete the same work in 12 days, in how many days can B alone complete that work?
A. 6 days
B. 4 days
C. 8 days
D. 9 days
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Q3. A is twice as good a workman as B and together they finish a piece of work in 18 days. In how many days will A alone finish the work?A. 27 days B. 24 daysC. 28 daysD. 29 days
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Q4. A and B working separately can do a piece of work in 9 and 12 days respectively. If they work for a day alternately, A beginning, in how many days, the work will be completed?A. 10 ¼ days B. 10 ½ daysC. 8 ¼ daysD. 8 ½ days
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Man- Days Concept
(N1*D1*H1)/W1 = (N2*D2*H2)/W2
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Examples : (Man-Days Concepts)Q5. 7 spiders can make 7 webs in 7 days. 1 spider will make 1 web in how many days?
A. 1 day B. 7 daysC. 14 daysD. 49 days
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Q6. 45 men can complete a work in 16 days. Six days after they started working, 30 more men joined them. How many days will they now take to complete the remaining work?A. 6 days B. 4 daysC. 8 daysD. 9 days
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Problems
Q7. A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?
A.14B.15C.16D.17
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Q8. A alone can do a piece of work in 6 days and B alone in 8 days. A and B undertook to do it for Rs. 3200. With the help of C, they completed the work in 3 days. How much is to be paid to C?
A.374B.400C.375D.None
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Q9. A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?
A.8 B.12C.16D.None
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Q10. 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 10 days and C alone in 50 days, then B alone could do it in:
A.15B.25C.30D.None
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Q11. If A can complete a work in 12 days, B in 15 days and C can do the same work in 20 days.
i) Working simultaneously they will finish the work in how many days.
ii)A started the work and left after 2 day the remaining work by B in how many days?
iii)A started the work and B joins after 3 days the remaining work will be completed in how many days
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iv) If A can complete a work in 12 days, B in 15 days and C can do the same work in 20 days.
v)They started the work together & C left after 2 days, the remaining work will be done in how many days.
vi)They started the work together and B left 2 days before the completion of work after how many days B left.
vii) Working alternatively (A, B, C, A, B, C…..) they will finish the work in how many days.
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Q12. If 36 Men can do the work in 18 days then the same work will be done by 18 Men in how many days?
A.32B.36C.18D.None
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Q13. 10 woman can complete a work in 7 days and 10 children take 14 days to complete the work. How many days will 5 woman and 10 children take to complete the work.
A.14B.7C.21D.None
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Q14. 10 woman can complete a work in 7 days, 10 children take 14 days and 10 men take 21 days to complete the work. How many days will 5 woman, 10 children and 15men take to complete the work?
A.6.67B.4.67C.5.67D.None
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Q15. A can complete a work in 10 days. B can complete it in 12 days. If they work on alternate days they can complete the work in how many days if-A starts the work
A.12.6B.11.6C.13.6D.None
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Division of wages (Concept)
The wages should be divided based on the work efficiency (no of chocolates eaten) and not the no of days
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Q16. A can do a piece of work in 30 days and B can do the same work in 50 days. If they both work together to complete the work and get a total of Rs 800. What should be the share of A and B
A.200,600B.300,500C.500,300D.None
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