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A and B together can dig a trench in 12 days, which A alone can dig in 28 days; B alone can dig it in
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- 20 days
- 21 days
- 22 days
- 23 days
Correct Option: B
B’s 1 day’s work = (A + B)’s 1 day’s work – A’s 1 day’s work
| B’s 1 day’s work = | - | = | 12 | 28 | 84 |
| B’s 1 day’s work = | = | 84 | 21 |
∴ Required time = 21 days
Second method to solve this question ,
| Time taken by B = | days | |
| x - y |
| Time taken by B = | ||
| 28 - 12 |
| Time taken by B = | = 21 days | |
| 16 |
