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Babu and Asha can do a job together in 7 days.
Asha is 1 3 times 4
as efficient as Babu. The same job can be done by Asha alone in
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49 days 4
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49 days 3 - 11 days
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28 days 3
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Correct Option: C
Ratio of efficiency of Babu and Asha
| = 1 : | = 4 : 7 | 4 |
As the time taken is inversely proportional to efficiency, therefore, if Babu takes 7x days to complete work, Asha will take 4x days.
| = | + | = | ||||
| 7x | 4x | 7 |
| ⇒ | = | |||
| 28x | 7 |
⇒ 28x = 11 × 7
| ⇒ x = | = | |||
| 28 | 4 |
∴ Asha will complete the work in
| 4x = 4 × | = 11 days | 4 |
Aliter : Using Rule 22,
| Here, n = | , D = 7 | 4 |
∴ Time taken by Asha
| = |  |  | × D days | n |
| = | | | × 7 | 7/4 |
| = | × 7 = 11 days | 4 |
