A leak at the bottom of a tank can empty the full tank in 6 hours. An inlet pipe fills water at the rate of 4 litres per minute. When the tank is full, the inlet is opened, and because of the leakage the tank becomes empty in 8 hours. What is the capacity of the tank, in litres?

Explanation

Let the tank capacity be C litres. The leak alone empties it in 360 minutes, so the leak rate is C/360 litres per minute. With a 4 L/min inlet open, the net emptying rate is C/480 litres per minute. Thus:
C/360 - 4 = C/480,
which gives C = 5760 litres.