Question 110

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 ?

Solution

(A + B + C)'s 1 day's work

= $$\frac{1}{20} + \frac{1}{30} + \frac{1}{60} = \frac{3 + 2 + 1}{60}$$

= $$\frac{1}{10}$$

A's 2 day's work = $$\frac{2}{20} = \frac{1}{10}$$

=> Work done in first 3 days = $$\frac{1}{10} + \frac{1}{10}$$

= $$\frac{2}{10} = \frac{1}{5}$$

Hence, the work will be finished in 15 days.

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