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. 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.


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