Question:
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
10 days
15 days
20 days
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].
[B].
[C].
[D].
Answer: Option B
Explanation:
| Work done by X in 4 days = | 1 | x 4 | = | 1 | . | ||
| 20 | 5 |
| Remaining work = | 1 – | 1 | = | 4 | . | ||
| 5 | 5 |
| (X + Y)’s 1 day’s work = | 1 | + | 1 | = | 8 | = | 2 | . | ||
| 20 | 12 | 60 | 15 |
| Now, | 2 | work is done by X and Y in 1 day. |
| 15 |
| So, | 4 | work will be done by X and Y in | 15 | x | 4 | = 6 days. | ||
| 5 | 2 | 5 |
Hence, total time taken = (6 + 4) days = 10 days.