X and Y can do a piece of work in 20 days and 12 days respectively. X started…
2025
X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?
- A.
6 days
- B.
10 days
- C.
15 days
- D.
20 days
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Correct answer: B
Solution:
X's one day work = 1/20. Y's one day work = 1/12.
Work done by X in the first 4 days = 4 × 1/20 = 1/5.
Remaining work = 1 − 1/5 = 4/5.
Combined one day work of X and Y = 1/20 + 1/12 = 2/15.
Time to finish the remaining 4/5 = (4/5) ÷ (2/15) = 6 days.
Total time = 4 days (initial) + 6 days = 10 days.
Answer: 10 days