Pipe Q can fill the tank in 60 hours while pipe R may fill in 45 hours. Q and R pipes are opened together for 6 hours after which pipe W is also opened to empty the tank. All three pipes are opened simultaneously for 24 hours to reach the half level mark. How much time (in hours) will pipe W alone take to empty the entire tank?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 36.
Let the capacity of the tank = LCM of 60 and 45 = 180 unit
Efficiency of Q = 180/60 = 3 unit/h, Efficiency of R = 180/45 = 4 unit/h
Tank filled by Q and R in 6 hours = (3 + 4) × 6 = 42 unit
According to the question,
= 24
⇒ 48/(7 - w) = 24
⇒ 2 = 7 - w
w = 5
So, pipe w can empty the tank = 180/5 = 36 hours