A pump can fill a tank with water in 4 hours. Because of a leak, it took 20 hours to fill the tank. The leak can drain all the water of the tank in?  Choose the correct choice from the following answers:
A) 1  B) 3  C) 5  D) 4  E) 2

Rationale: p - - > pump , l - - - > leak pipe - - - - - - - - - - p - - - - - - - - - l - - - - - - - - - - - - ( p - l ) - - time - - - - - - - - - 4 - - - - - - - - - x - - - - - - - - - - - - - 20 * rate - - - - - - - - - 5 - - - - - - - - - x - - - - - - - - - - - - - 1 work - - - - - - - 20 - - - - - - - - - 20 - - - - - - - - - - - 20 time required to empty the tank if leakage present = 20 / ( ( 5 ) - 1 ) = ( 20 ) / ( 4 ) = 5 ans - c
Answer: C