Two taps X and Y are fixed to a water tank. If only X is opened, it drains out the full tank of water in 20 minutes. If both X and Y are opened, then they drain out the full tank of water in 15 minutes. If only Y is opened, how long does it take to drain out the full tank of water?

Two taps X and Y are fixed to a water tank. If only X is opened, it dr

1.	Two taps X and Y are fixed to a water tank. If only X is opened, it drains out the full tank of water in 20 minutes. If both X and Y are opened, then they drain out the full tank of water in 15 minutes. If only Y is opened, how long does it take to drain out the full tank of water?
A.	30 minutes
B.	45 minutes
C.	60 minutes
D.	90 minutes
Answer» D. 90 minutes