Pipe A can fill a tank in 12 minutes; pipe B can fill it in 18 minutes, and pipe C can empty the full tank in 36 minutes. If all the pipes are opened simultaneously, how much time will it take to fill the empty tank completely?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 9 minutes.
Given:
Pipe A can fill a tank in 12 minute
Pipe B can fill it in 18 minutes
Pipe C can empty the full tank in 36 minutes
Concept Used:
Total work = Efficiency × Time
Explanation:
Let the capacity of the tank be LCM (12, 18, 36) = 36 units
The efficiency of pipe A to fill the tank = 36/12 = 3
The efficiency of pipe B to fill the tank = 36/18 = 2
The efficiency of pipe C to empty the tank = 36/36 = 1
The tank is filled by all pipes together in 1 minute = 3 + 2 - 1 = 4 units
Hence, the tank is completely filled by all pipes together in = 36/4 = 9 minutes