Pipe A can fill a tank in 10 hours, Pipe B in 20 hours. Pipe C can empty the full tank in 25 hours. If all are opened together, how long will it take to fill the tank?
Show answer & explanation
Correct answer: A
Explanation
Rate of A = 1/10
Rate of B = 1/20
Rate of C = -1/25
Net rate = 1/10 + 1/20 − 1/25
= (10 + 5 − 4)/100
= 11/100
Therefore, time = 100/11 = 9.09 hours