What was the question for this implicit rationale, and corresponding answer?
In 1 hour it fill 1/20 + 1/12 - 1/20 = 1/12
So fill tank fill up in 12 Hours
The answer: (E)
The question: Two pipes can fill a tank in 20 and 12 hours, while third pipe will make the tank empty in 20 hours. If all three pipes operate simultaneously. In how many hours the tank will be filled ?
Options:
(A) 5 Hours
(B) 7 Hours
(C) 8 Hours
(D) 9 Hours
(E) 12 Hours