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?
8
7
4
5
Explanation:
Given,
(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.