Two pipes can fill a tank in 10 hours and 12 hours respectively while a third pipe empties the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time will the tank be filled?

Two pipes can fill a tank in 10 hours and 12 hours respectively while

1.	Two pipes can fill a tank in 10 hours and 12 hours respectively while a third pipe empties the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time will the tank be filled?
A.	5 hour 20 minutes
B.	6 hour 15 minutes
C.	7 hour 30 minutes
D.	8 hour 20 minutes
Answer» D. 8 hour 20 minutes