1.  A does a work in 10 days and B does the same work in 15 days. in how many days they together will do the same work?
A. 5 days
B. 6 days
C. 8 days
D. 9 days

Answer: Option B

Explanation:

A's 1 days work=1/10 and B 's 1 days work = 1/15.

∴ (A + B)'s 1 day's work = 1/10 + 1/15 = 1/6.

So, both together will finish the work in 6 days.