Two pipes A and B can fill a cistern in 37½ minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:

Question

Accepted Answer

Let B be turned off after x minutes. Then, Part filled by (A + B) in x min. + Part filled by A in (30 -x) min. = 1. ∴ x …

∴ x	❨	2	+	1	❩	+ (30 - x).	2	= 1
		75		45			75

⟹	11x	+	(60 -2x)	= 1
	225		75

Two pipes A and B can fill a cistern in 37½ minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:

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