A pump can fill a tank with a water in 2 hours. Because of a leak, it took 2 and 4/5 hours to fill the tank. The leak can drain all the water of the full tank in how many hours? Choose the correct choice from the following answers: A) 4 B) 5 C) 6 D) 7 E) 8
The rate of the pump + leak = 5/14   1/2 - leak's rate = 5/14   leak's rate = 1/2 - 5/14 = 1/7   The leak will empty the tank in 7 hours.   The answer is 7.
<result>D</result>
A pump can fill a tank with a water in 2 hours. Because of a leak, it took 2 and 4/5 hours to fill the tank. The leak can drain all the water of the full tank in how many hours?