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 |
[B].
10 days |
[C].
15 days |
[D].
20 days |
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.
