An electric pump can fill a tank in 3 hours. Because of a leak in the tank, it took 12 hours to fill the tank. If the tank is full, how much time will the leak take to empty it?
Pick:	A) 4 hours	B) 12hours	C) 8hours	D) 5hours	E) 15hours
Work done by the leak in 1 hour = 1/3 - 1/12 = 1/4   The leak will empty the tank in 4hours   4 hoursnswer is 4 hours
<result>A</result>
An electric pump can fill a tank in 3 hours. Because of a leak in the tank, it took 12 hours to fill the tank. If the tank is full, how much time will the leak take to empty it?