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Two pipes can fill a cistern in 3 hours and 4 hours respectively and a waste pipe can empty it in 2 hours. If all the three pipes are kept open, then the cistern will be filled in :
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- 5 hours
- 8 hours
- 10 hours
- 12 hours
- 5 hours
Correct Option: D
As per the given in question , we have
Cistern filled by 1st pipe + Cistern filled by 2nd pipe – Cistern emptied by 3rd pipe
| Part of the cistern filled in 1 hour = | + | - | |||
| 3 | 4 | 2 |
| Part of the cistern filled in 1 hour = | = | ||
| 12 | 12 |
Hence, the cistern will be filled in 12 hours.
