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A tap can fill a cistern in 40 minutes and a second tap can empty the filled cistern in 60 minutes. By mistake without closing the second tap, the first tap was opened. In how many minutes will the empty cistern be filled ?
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- 72
- 84
- 108
- 120
- 72
Correct Option: D
From the given question ,
| ∴ Part of the cistern filled by first tap in 1 minute = | ||
| 40 |
| ∴ Part of the cistern emptied by second tap in 1 minute = | ||
| 60 |
| ∴ Part of the cistern filled in 1 minute by both the tapes = | - | = | = | ||||
| 40 | 60 | 120 | 120 |
∴ Empty cistern will be filled in 120 minutes.
