A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is?	Choose the correct answer.
A) 8	B) 8/11	C) 8/13	D) 8/15	E) None
A's 1 day's work =	1	;   15   B's 1 day's work =	1	;   20   (A + B)'s 1 day's work =	(	1	+	1	)	=	7	.   15	20	60   (A + B)'s 4 day's work =	(	7	x 4	)	=	7	.   60	15   Therefore, Remaining work =	(	1 -	7	)	=	8	.   15	15   Option 8/15
<result>D</result>
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is?