1.  A can do a piece of work in 20 days which B can do in 12 days. B worked at it for 9 days. A can finish the remaining work in ?
A. 3 days
B. 5 days
C. 7 days
D. 11 days

Answer: Option B

Explanation:

B's 9 day's work = 9 x (1/12) = 3/4

Remaining work = (1 - 3/4) = 1/4

∴ 1/4 work is done by A in = 20 x (1/4) = 5 days.