A leak in the bottom of a tank can empty the full tank in 4 hours. An inlet pipe fills water at the rate of 6 litres a minute. When the tank is full, the inlet is opened and due to the leak, the tank is empty in 12 hours. How many litres does the cistern hold?
Options:
A) 7580
B) 7960
C) 8290
D) 2160
E) None
Solution   Work done by the inlet in 1 hour	= (1/4 - 1/12)   = 1/6.   Work done by the inlet in 1 min.	= (1/6 × 1/60)   = 0.002778   Volume of 0.002778 part = 6 litres.   Therefore, Volume of whole	= (.002778×6)   ‹=› 2160 litres.   Answer 2160
<result>D</result>
A leak in the bottom of a tank can empty the full tank in 4 hours. An inlet pipe fills water at the rate of 6 litres a minute. When the tank is full, the inlet is opened and due to the leak, the tank is empty in 12 hours. How many litres does the cistern hold?