Two pipes X and Y can ﬁll a cistern in 6 hours and 10 hours respectively. Pipe Z can empty the tank in 4 hours. If all the three pipes are opened together then in how many hours the cistern will be full?

Two pipes X and Y can ﬁll a cistern in 6 hours and 10 hours respecti

1.	Two pipes X and Y can ﬁll a cistern in 6 hours and 10 hours respectively. Pipe Z can empty the tank in 4 hours. If all the three pipes are opened together then in how many hours the cistern will be full?
A.	30
B.	45
C.	50
D.	60
Answer» E.