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A cistern can be filled by two pipes A and B in 4 hours and 6 hours respectively. When full, the tank can be emptied by a third pipe C in 8 hours . If all the taps be turned on at the same time, the cistern will be full in ?
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- 3 hours 18 min.
- 3 hours 26 min.
- 3 hours 42 min.
- 3 hours 48 min.
Correct Option: B
Net filling in 1 hour = (1/4 + 1/6 - 1/8) = 7/24
∴ Time taken to fill the cistern = (24/7) hrs. = 3 hrs. 26 min.
