X can do a piece of work in 40 days. He works at it for 8 days and then Y finished it in 16 days. How long will they together take to complete the work?

Answer: Option A

Explanation:

Work done by X in 8 days =		1	x 8		=	1	.
		40				5

Remaining work =		1 -	1		=	4	.
			5			5

Now,	4	work is done by Y in 16 days.
	5

Whole work will be done by Y in		16 x	5		= 20 days.
			4

X's 1 day's work =	1	, Y's 1 day's work =	1	.
	40		20

(X + Y)'s 1 day's work =		1	+	1		=	3	.
		40		20			40

Hence, X and Y will together complete the work in		40		= 13	1	days.
		3			3