Question: A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
[A].23 days
37 days
37
40 days
[A].
[B].
[C].
[D].
Answer: Option C
Explanation:
| Whole work is done by A in | 20 x | 5 | = 25 days. | ||
| 4 |
| Now, | 1 – | 4 | i.e., | 1 | work is done by A and B in 3 days. | ||
| 5 | 5 |
Whole work will be done by A and B in (3 x 5) = 15 days.
| A’s 1 day’s work = | 1 | , (A + B)’s 1 day’s work = | 1 | . |
| 25 | 15 |
| B’s 1 day’s work = | 1 | – | 1 | = | 4 | = | 2 | . | ||
| 15 | 25 | 150 | 75 |
| So, B alone would do the work in | 75 | = 37 | 1 | days. |
| 2 | 2 |