P and Q together can complete a piece of work in 4 days. If P alone can complete the same work in 20 days, in how many days can Q alone complete that work?
Pick one:
A) 2	B) 7	C) 5	D) 9	E) 1
Explanation:   (P + Q)'s 1 day's work = 1/4, P's 1 day's work = 1/20   Q's 1 day's work = (1/4 – 1/20) = (4/20) = (1/5)   Hence, Q alone can complete the work in 5 days.   ANSWER: 5
<result>C</result>
P and Q together can complete a piece of work in 4 days. If P alone can complete the same work in 20 days, in how many days can Q alone complete that work?