A can do a piece of work in 10 days and B can do the same piece of work in 20 days. They start the work together but after 5 days A leaves off, B will do the remaining piece of work in?
Correct Answer: 5 days
Explanation:
(A + B)'s 5 day's work = 5 x (1/10 + 1/20) = 3/4
Remaining work = (1 - 3/4) = 1/4
1/20 work is done by B in = 1 day
∴ 1/4 work is done by B in = 20 x (1/4) i.e., 5 days.