Question

12. A cistern can be filled by pipes A and B in 4 hours and 6 hours respectively. When full, the cistern
can be emptied by a pipe C in 8 hours. If all the pipes be turned on at the same time, the cistern
will be full in
(a) 3 hrs 18 min (b) 3 hrs 26 min (c) 3 hrs 42 min (d) 3 hrs 48 min​
(please explain the answer and I will mark it brainliest)

Answer 1

Step-by-step explanation:

Part filled in 1 hr = (1/4 + 1/6) = 5/12, Part emptied in 1 hr = 1/8

Net filling in 1 hr = (5/12 - 1/8) = 7/24

therefore

Time taken to fill the tank = 24/7 hr

= 3 hours 26 minute