Question: A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
[A].
[A].
| 1 |
| 4 |
[B].
| 1 |
| 10 |
[C].
| 7 |
| 15 |
[D].
| 8 |
| 15 |
Answer: Option D
Explanation:
| A’s 1 day’s work = | 1 | ; |
| 15 |
| B’s 1 day’s work = | 1 | ; |
| 20 |
| (A + B)’s 1 day’s work = | 1 | + | 1 | = | 7 | . | ||
| 15 | 20 | 60 |
| (A + B)’s 4 day’s work = | 7 | x 4 | = | 7 | . | ||
| 60 | 15 |
| Therefore, Remaining work = | 1 – | 7 | = | 8 | . | ||
| 15 | 15 |