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 option:  A) 12 days  B) 15 days  C) 16 days  D) 18 days  E) none
A's 2 day's work = (1/20 * 2) = 1/10   (A + B + C)'s 1 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.   Whole work will be done in (3 x 5) = 15 days.   Answer = 15 days
<result>B</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?