A pump can fill a tank with water in 4 hours. Because of a leak, it took 7 hours to fill the tank. The leak can drain all the water in ? Select:
A) 15hr 10min B) 16hr 20min C) 9hr 20min D) 15hr E) 14hr 25min
Work done by the leak in 1 hour = 1/4 - 1/7 = 3/28   Leak will empty the tank in 28/3 hrs = 9hr 20min   Answer is 9hr 20min
<result>C</result>
A pump can fill a tank with water in 4 hours. Because of a leak, it took 7 hours to fill the tank. The leak can drain all the water in ?