Two pipes can fill a tank in 30 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 ?\nOptions:\n(A) 5 Hours\n(B) 7 Hours\n(C) 8 Hours\n(D) 9 Hours\n(E) 15 Hours Stream of consciousness first, then make a decision:
User
In 1 hour it fill 1/30 + 1/12 - 1/20 = 1/15\nSo fill tank fill up in 15 Hours
Thus, the answer is (E).
Assistant