A pump can fill a tank with a water in 2 hours. Because of a leak, it took 3 hours to fill the tank. The leak can drain all the water of the full tank in how many hours?	Choose one.
A) 2 B) 3 C) 4 D) 5 E) 6
The rate of the pump + leak = 1/3   1/2 - leak's rate = 1/3   leak's rate = 1/2 - 1/3 = 1/6   The leak will empty the tank in 6 hours.   The answer is 6.
<result>E</result>
A pump can fill a tank with a water in 2 hours. Because of a leak, it took 3 hours to fill the tank. The leak can drain all the water of the full tank in how many hours?