Two inlet pipes P and Q can fill a tank in 10 hours and 12 hours separately. There is an outlet R that can let out water from the tank fully in 30 hours. If all the pipes are opened simultaneously, how much time will it take to fill the tank completely?

Two inlet pipes P and Q can fill a tank in 10 hours and 12 hours separ

1.	Two inlet pipes P and Q can fill a tank in 10 hours and 12 hours separately. There is an outlet R that can let out water from the tank fully in 30 hours. If all the pipes are opened simultaneously, how much time will it take to fill the tank completely?
A.	6 hours 40 minutes
B.	6 hours 30 minutes
C.	14 hours 45 minutes
D.	5 hours 30 minutes
Answer» B. 6 hours 30 minutes