P is able to do a piece of work in 15 days and Q can do the same work in 20 days. If they can work together for 4 days, what is the fraction of work left?	Pick one:
A) 8/15
B) 7/15
C) 1/15
D) 3/15
E) None of these
Explanation:   P's 1-day work = 1/15   Q's 1-day work = 1/20   Work done by (P + Q) in 1 day = 1/15 + 1/20 = 7/60.   Work done by them in 4 days = (7/60) * 4 = 7/15.   Work left = 1 - (7/15) = 8/15.   8/15NSWER IS 8/15
<result>A</result>
P is able to do a piece of work in 15 days and Q can do the same work in 20 days. If they can work together for 4 days, what is the fraction of work left?