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, B and C can do a piece of work in 20, 30 and 60 days respectively.

1.	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.	12 days
B.	15 days
C.	16 days
D.	18 days
Answer» B. 15 days