Question

A, B and C together can finish a piece of work in 4 days, A alone can do it in 12 days and B alone in 18 days. How many days will be taken by C to do it alone?

Answer 1

9 days

Explanation:

Let x = days taken by C to do it alone

In one day, A can do: 1/12 (part of the whole work)

In one day, B can do: 1/18 (part of the whole work)

In one day, C can do: 1/x (part of the whole work)

In one day,together A, B and C can do: 1/4 (part of the whole work)

we have this equation:

1/x + 1/12 + 1/18 = 1/4

--> 1/x = 1/4 - 1/12 - 1/18 = 1/9

--> x = 9 (days)