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?
Pick:
A) 10 days  B) 12 days  C) 15 days  D) 20 days  E) 25 days
A's 2 day's work = 1	x 2 =	1	.   20	10   (A + B + C)'s 1 day's work = 1	+	1	+	1 =	6	=	1	.   20	30	60	60	10   Work done in 3 days = 1	+	1 =	1	.   10	10	5   Now,	1	work is done in 3 days.   5   Whole work will be done in (3 x 5) = 15 days.   Option 15 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?