A tap can fill a cistern in 8 hours and another tap can

A tap can fill a cistern in 8 hours and another tap can empty it in 16 hours. If both the taps are open, the time (in hours) taken to fill the tank will be :

Part of the cistern filled in 1 hour =	1
	8

Part of the cistern emptied in 1 hour =	1
	16

When both the taps are opened simultaneously,

Part of cistern filled in 1 hour =	1	-	1	=	2 - 1	=	1
	8		16		16		16

Hence, the cistern will be filled in 16 hours.
We can find required answer with the help of given formula :
Here, p = 8, q = 16

Required time =	pq
	q - p

Required time =	8 × 16
	16 - 8

Required time = 16 hours