Two pipes can fill a cistern in 25 min and 20 min respectively. A third pipe can empty it in 10 minutes. Find out how much time will it take to empty a filled cistern, if all the pipes are opened all together?

Two pipes can fill a cistern in 25 min and 20 min respectively. A thir

1.	Two pipes can fill a cistern in 25 min and 20 min respectively. A third pipe can empty it in 10 minutes. Find out how much time will it take to empty a filled cistern, if all the pipes are opened all together?
A.	80 min
B.	75 min
C.	50 min
D.	100 min
E.	None of these
Answer» E. None of these