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Two pipes A and B can fill a tank in 36 minutes and 45 minutes respectively. Another pipe C can empty the tank in 30 minutes. First A and B are opened. After 7 minutes, C is also opened. The tank is filled up in
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- 39 minutes
- 46 minutes
- 40 minutes
- 45 minutes
- 39 minutes
Correct Option: B
As per the given in question , we have
| Part of the tank filled by pipes A and B in 1 minute = | + | = | = | = | |||||
| 36 | 45 | 180 | 180 | 20 |
| Part of the tank filled by these pipes in 7 minutes = | ||
| 20 |
| Remaining unfilled part = 1 – | = | = | |||
| 20 | 20 | 20 |
When all three pipes are opened.
| = | - | = | = | ||||
| 20 | 30 | 60 | 60 |
| ∴ Time taken in filling | part | = | × 60 = 39 minutes | ||
| 20 | 20 |
Required time = 39 + 7 = 46 minutes
