Two pipes A and B can fill a cistern in 3 hours and 5 hours

Two pipes A and B can fill a cistern in 3 hours and 5 hours respectively. Pipe C can empty in 2 hours. If all the three pipes are open, in how many hours the cistern will be full?

As per the given in question , we have

Part of cistern filled by two pipes in an hour =	1	+	1
	3		5

Part of the tank emptied in 1 hour by pipe C =	1
	2

Part of cistern filled by three pipes in an hour =	1	+	1	-	1	=	10 + 6 - 15	=	1
	3		5		2		30		30

Hence, the cistern will be filled in 30 hours.