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? Pick:
A) 1/4	B) 1/10	C) 7/15	D) 8/15	E) 9/13
Explanation:   A’s one day work = 1/15   B’s one day work = 1/20   (A+B )’s one day work is = 1/15 +1/20 = 7/60   their 4 days work = 4 x 7/60 = 7/15   Remaining work = 8/15   Answer: 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?