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A and B together can do a work in 12 days. B and C together do it in 15 days. If A’s efficiency is twice that of C, then the days required for B alone to finish the work is
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- 60 days
- 30 days
- 20 days
- 15 days
Correct Option: C
(A + B)’s 1 day’s work
| = | .............(i) | 12 |
(B + C)’s 1 day’s work
| = | .............(ii) | 15 |
∴ Difference between A and C’s 1 day’s work
| - | = | = | ||||||
| 12 | 15 | 60 | 60 |
If A alone completes the work in x days, C will do the same in 2x days.
| ∴ | - | = | ||||
| x | 2x | 60 |
| ⇒ | = | |||
| 2x | 60 |
| ⇒ | = | |||
| 2x | 60 |
⇒ x = 30
∴ B’s 1 day’s work
| = | - | [From equation (i)] | ||
| 12 | 30 |
| = | = | = | ||||
| 60 | 60 | 20 |
Hence, B alone will complete the work in 20 days.
