Time and Work problems
- 1. 20 persons completed 1/3rd of the work in 12 days. How many more person are required to finish the rest work in next 12 days?
Options- A. 20
- B. 12
- C. 18
- D. 40 Discuss
Correct Answer: 20
Explanation:
Work done = 1/3
Remaining work = 2/3
So for double work in same days we need double number of people i.e. 40.
So, 20 men will be increased.
- 2. A and B can together do a piece of work in 15 days. B alone can do it 20 days. In how many days can A alone do it?
Options- A. 30 days
- B. 40 days
- C. 45 days
- D. 60 days Discuss
Correct Answer: 60 days
Explanation:
A's 1 day's work = (1/15 - 1/20) = 1/60
? A alone can finish it in 60 days.
- 3. A and B can do a piece of work in 6 days and A alone can do it in 9 days. The time taken by B alone to do the same work is?
Options- A. 18 days
- B. 15 days
- C. 12 days
- D. 71/2 Discuss
Correct Answer: 18 days
Explanation:
B's one day's work = (1/6 - 1/9) = 1/18
? B alone can finish it in 18 days.
- 4. A and B can do a piece of work in 18 days, B and C in 24 days, A and C in 36 days. In what time can they do it all working together?
Options- A. 12 days
- B. 13 days
- C. 16 days
- D. 26 days Also asked in: Bank Exams
Correct Answer: 16 days
Explanation:
(A + B)'s 1 day's work = 1/18
(B + C)'s 1 day's work = 1/24
(A + C)'s 1 day's work = 1/36
Adding 2 (A + B + C)'s 1 day's work = (1/18 + 1/24 + 1/36) = 1/8
? (A + B + C)'s day's work = 1/16
Hence, all working together can finish it in 16 days.
- 5. A and B can do a piece of work in 12 days. B and C in 15 days. C and A in 20 days. A alone can do the work in?
Options- A. 152/3
- B. 24 days
- C. 30 days
- D. 4 days Discuss
Correct Answer: 30 days
Explanation:
? [(A + B) + (B + C) + (C + A)]'s 1 day's work = (1/12 + 1/15 + 1/20) = 1/5
? 2(A + B + C)'s 1 days work = 1/5
? (A + B + C)'s 1 day's work = 1/10
&rArr A's 1 day's work = (1/10 - 1/15) = 1/30
? A alone can finish it in 30 days.
- 6. A can do a piece of work in 30 days while B can do it in 40 days. In how many days can A and B working together do it?
Options- A. 70 days
- B. 423/4 days
- C. 271/7 days
- D. 171/7 days Discuss
Correct Answer: 171/7 days
Explanation:
(A + B)'s 1 day's work = (1/30 + 1/40) = 7/120
? Time taken by both to finish the work = 120/7days = 171/7 days
- 7. A can do (1/3) of a work in 5 days and B can do (2/5) of the work in 10 days. In how many days both A and B together can do the work?
Options- A. 73/4
- B. 84/5
- C. 93/8
- D. 10 Discuss
Correct Answer: 93/8
Explanation:
? 1/3 of work is done by A in 5 days.
? Whole work will be done by A in 15 days.
? 2/3 of work is done by B in 10 days.
Whole work will be done by B in 10 x (5/2) i.e., 25days
? (A + B)'s 1 day's work = (1/15 + 1/25) = 8/75
So, both together can finish it in 75/8 days, i.e., 93/8days.
- 8. A can do a piece of work in 20 days which B can do in 12 days. B worked at it for 9 days. A can finish the remaining work in?
Options- A. 3 days
- B. 5 days
- C. 7 days
- D. 11 days Discuss
Correct Answer: 5 days
Explanation:
B's 9 day's work = 9 x (1/12) = 3/4
Remaining work = (1 - 3/4) = 1/4
1/4 work is done by A in = 20 x (1/4) = 5 days.
- 9. 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?
Options- A. 12 days
- B. 20 days
- C. 24 days
- D. 28 days Discuss
Correct Answer: 24 days
Explanation:
Required time taken by B to complete the work = xy / x - y
[Here x = 12 and y = 8]
? required time = (12 x 8) / (12 - 8) = 96/4 = 24 days
- 10. Rohan and Sunil separately can complete a work in 8 hours and 4 hours respectively. How much time will they take when working together?
Options- A. 22/3
- B. 11/3
- C. 3 hours
- D. 2 hours Discuss
Correct Answer: 22/3
Explanation:
Required time taken to complete the work by both together = x y / x + y
(Here x = 8 and y = 4)
? Required time = (8 x 4)/(8 + 4) = 32/12 = 22/3 hours
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