Question

A cistern can be filled by pipes a and b in 4 hours and 6 hours respectively. when full, the tank can be emptied by a pipe c in 8 hours. if all the taps be turned on at the same time , the cistern will be full in :

Answer 1

Pipe A can fill a tank in 4 hours
Pipe A in 1 hour fill 1/4 of the tank

Pipe B can fill a tank in 6 hours
Pipe B in 1 hour can fill 1/6 of the tank

Pipe C can empty a tank in 8 hours
Pipe C in 1 hour can empty 1/8 of the tank

All the three pipes are opened together.In 1 hour,
they fill: 1/4 + 1/6 - 1/8 = 6+4-3/24 = 7/24 of the tank  [-1/8 coz it is emptying]
Hence tank will be full in 24/7 hours or 3 3/7 hours

Answer 2

Answer:

3hrs 42 min

Step-by-step explanation:

a+b then result - c