Three pipes A, B and C can fill a cistern in 6 hours. After

Three pipes A, B and C can fill a cistern in 6 hours. After working at it together for 2 hours, C is closed and A and B fill it in 7 hours more. The time taken by C alone to fill the cistern is

On the basis of given details in question ,

Part of the cistern filled by pipes A, B and C in 1 hour =	1
	6

∴ Part of the cistern filled by all three pipes in 2 hours =	1
	3

∴ Remaining part = 1 –	1	=	2
	3		3

Now, pipe A and B fill 2/3 part of the cistern in 7 hours

∴ Pipe A and B will fill the cistern in	7 × 3	=	21	hours
	2		2

∴ Part of the cistern filled by A and B in 1 hour =	2
	21

So , Part of the cistern filled by C in 1 hour =	1	-	2
	6		21

Part of the cistern filled by C in 1 hour =	7 - 4	=	1
	42		14

∴ Pipe C will fill the cistern in 14 hours.