An inlet pipe can fill an empty tank in 51 hours while an outlet pipe drains a completely-filled tank in 76.5 hours. If both the pipes are opened simultaneously when the tank is empty, in how many hours will the tank get completely filled?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 153.
Let the total work to be done (LCM of 51 and 76.5) be 153 units.
Efficiency of inlet pipe = 153/51 = 3 units/hour
Efficiency of outlet pipe = 153/76.5 = 2 units/hour
Efficiency of both inlet and outlet pipes together = 3 - 2 = 1 unit/hour
Time taken to fill the tank when both pipes are opened together = 153/1 = 153 hours