A tank can be filled with water by two pipes A and B together

A tank can be filled with water by two pipes A and B together in 36 minutes. If the pipe B was stopped after 30 minutes, the tank is filled in 40 minutes. The pipe B can alone fill the tank in

Let the pipe B fill the tank in t minutes.

Part of the tank filled by pipes A and B in 1 minute =	1
	36

∴ Part of the tank filled by pipe A in 1 minute =	1	-	1
	36		t

According to the question,

30 ×	1	+ 40		1	-	1		= 1
	t			36		t

⇒	30	+	10	-	40	= 1
	t		9		t

⇒	40	-	30	=	10	- 1
	t		t		9

⇒	10	=	1	⇒ t = 90 minutes
	t		9