# A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day ?

A. 18

B. 12

C. 15

D. 14

**Answer : **C. 15

## Explanation:

A's 2 day's work = 1/20 x 2

= 1/10

(A + B + C) 1 day's Work = (1/20 + 1/30 + 1/60)

= 6/60

= 1/10

Now,

Work done in 3 days = (1/10) + (1/10)

= 1/5

Now 1/5 work is done in 3 days.

Now whole work will be done in **3 * 5 = 15 days**.