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A and B working separately can do a piece of work in 9 and 15 days respectively. If they work for a day alternately, with A beginning, then the work will be completed in
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- 10 days
- 11 days
- 9 days
- 12 days
Correct Option: B
| A’s 1 day’s work = | ||
| 9 |
| B’s 1 day’s work = | ||
| 15 |
Work done in first 2 days = A’s 1 day’s work + B’s 1 day’s work
| Work done in first 2 days = | + | 9 | 15 |
| Work done in first 2 days = | = | 45 | 45 |
| ∴ Work done in first 10 days = | = | 45 | 9 |
| Remaining work = 1 – | = | 9 | 9 |
Now, it is turn of ‘A’ for the eleventh day.
| ∴ Time taken by ‘A’ in doing | work | |
| 9 |
| = | × 9 = 1 day | |
| 9 |
∴ Required time = 10 + 1 = 11 days
