Two inlet pipes, one of which is twice the efficiency of the other. There is also a third outlet pipe which can empty the fully filled tank in 10 hours. When all three pipes are open simultaneously, it takes 2.5 hours to fill the tank completely. How many hours will it take to fill the tank alone with a low efficiency pipe?

Two inlet pipes, one of which is twice the efficiency of the other. Th

1.	Two inlet pipes, one of which is twice the efficiency of the other. There is also a third outlet pipe which can empty the fully filled tank in 10 hours. When all three pipes are open simultaneously, it takes 2.5 hours to fill the tank completely. How many hours will it take to fill the tank alone with a low efficiency pipe?
A.	7
B.	5
C.	8
D.	6
Answer» E.