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?	Choose the correct answer.
A) 12 days
B) 15 days
C) 18 days
D) 20 days
E) 22 days
A’s two day’s work = 2/20 = 1/10   (A + B + C)’s one day’s work = 1/20 + 1/30 + 1/60 = 6/60 = 1/10   Work done in 3 days = (1/10 + 1/10) = 1/5   Now, 1/5 work is done in 3 days   Therefore, Whole work will be done in (3 x 5) = 15 days.   ANSWER:18 days
<result>C</result>
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?