Three pipes of same capacity can fill a tank in 8 hours. If there are only two pipes of same capacity, the tank can be filled in.
Choose the correct choice from the following:
A) 11 hours  B) 12 hours  C) 15 hours  D) 16 hours  E) 17 hours

Rationale: the part of the tank filled by three pipes in one hour = 1 / 8 = > the part of the tank filled by two pipes in 1 hour = 2 / 3 * 1 / 8 = 1 / 12 . the tank can be filled in 12 hours . answer : b
Answer: B