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 choice from the following options:
A) 1/4 B) 1/10 C) 7/15 D) 8/15 E) 1/15
A's 1 day's work =1/15   B's 1 day's work =1/20   (A + B)'s 1 day's work =(1/15+1/20)=7/60,   (A + B)'s 4 day's work =(7/60x 4)=7/15.   Therefore, Remaining work =(1-7/15) = 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