-
A can do a piece of work in 40 days. He works on it for 5 days and then B completes it in 21 days. How long will A and B together take to complete the work?
-
- 10 days
- 15 days
- 20 days
- 25 days
Correct Option: B
Using Rule 2,
| A’s 1 day’s work = | 40 |
∴ A’s 5 days’ work
| = | = | |||
| 40 | 8 |
Remaining work
| = 1 - | = | |||
| 8 | 8 |
This part of work is done by B in 21 days.
∴ B’s 1 day’s work
| = | = | |||
| 8 × 21 | 24 |
∴ (A + B)’s 1 day’s work
| = | + | = | ||||
| 40 | 24 | 120 |
| = | = | |||
| 120 | 15 |
Hence, A and B together will
complete the work in 15 days.
