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Ganga and Saraswati, working separately can mow a field in 8 and 12 hours respectively. If they work in stretches of one hour alternately, Ganga beginning at 9 a.m., when will the moving be completed ?
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- 6 p.m.
- 6.30 p.m.
- 5 p.m.
- 5.30 p.m.
Correct Option: B
Part of the field mowed by
Ganga and Saraswati in first 2 hours
| = | + | = | = | |||||
| 8 | 12 | 24 | 24 |
∴ Part of the field mowed in first 8 hours
| = | = | = | ||||
| 24 | 24 | 6 |
Remaining work
| = 1 - | = | |||
| 6 | 6 |
Now, it is the turn of Ganga, part of work done by Ganga in 1 hour
| = | 8 |
Remaining work
| = | - | |||
| 6 | 8 |
| = | = | |||
| 24 | 24 |
Now, time taken by Saraswati in completing this part of work
| = | × 12 = | hour | ||
| 24 | 2 |
| ∴ Total time = 9 | hours | 2 |
The mowing starts at 9 am.
Hence, the mowing will be completed at 6.30 pm.
