A leak can empty a tank in 6 hours. An inlet pipe fills it at 4 litres per minute. When the tank is full, the inlet pipe remains open and, due to the leak, the tank is emptied in 8 hours. What is the capacity of the tank in litres?

Explanation

The leak empties 1/6 of the tank per hour, while the net emptying rate with the inlet open is 1/8 of the tank per hour. Therefore, the inlet fills 1/6 - 1/8 = 1/24 of the tank per hour. At 4 litres per minute, the inlet supplies 240 litres per hour, so 1/24 of the tank is 240 litres. The tank capacity is 240 × 24 = 5760 litres.