1.  A can do  of a work in 5 days and B can do  of the work in 10 days. In how many days both A and B together can do the work ?
A. 73/4 days
B. 84/5 days
C. 93/8 days
D. 10 days

Answer: Option C

Explanation:

∵ 1/3 of work is done by A in 5 days.

∴ Whole work will be done by A in 15 days.

∵ 2/3 of work is done by B in 10 days.

Whole work will be done by B in 10 x (5/2) i.e., 25days

∴ (A + B)'s 1 day's work = (1/15 + 1/25) = 8/75

So, both together can finish it in 75/8 days, i.e., 93/8 days.