A can finish a piece work in 18 days and B can do the same work in half the time taken by A. So if they working together, what part of the same work can finished in a day?

A can finish a piece work in 18 days and B can do the same work in half the time taken by A. So if they working together, what part of the same work can finished in a day?

A. 1/7
B. 1/6
C. 6
D. 5/6












Answer: Option B

Explanation:
First find the 1 day work of both (A & B)
A's 1 day's work = 1/18
and 
B's 1 day's work = 1/9 (B can do work in half time)
(A + B)'s 1 day's work = (1/18+1/9) 
= (1+2)/18 = 3/18 = 1/6 
so A & B together can do 1/6 of work in 1 day