Multiple choice

A leak in the bottom of a tank can empty a full tank in 7 hours. An inlet pipe fills water in the tank at the rate of 2 litres per minute. When the tank is full, the inlet is opened and due to the leak, the tank is emptied in 10.5 hours. The capacity of the tank is

  1. 2520 litres

  2. 3760 litres

  3. 2836 litres

  4. 2250 litres
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Leak rate = 1/7 tank/hr. Let inlet rate be I. Net rate = I - 1/7 = -1/10.5 = -1/(21/2) = -2/21. I = 1/7 - 2/21 = 3/21 - 2/21 = 1/21. Inlet fills 1/21 tank per hour. Inlet rate = 2 L/min = 120 L/hr. 1/21 capacity = 120 L, so capacity = 120 * 21 = 2520 litres.

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