Question

A and b working alone can do a work in 20 days and 15 days respectively. they started the work together but b left after sometime and a finished remaining work in 6 days. find after how many days from start b left the work

Answer 1

According to the question it is said that if a is working alone than he can complete the work in 20 days.

So we can write that in one day a can finish 1/20th part of the work.

In case of B it is said that he can finish the work in 15 days that means in one day he can finish 1/15th part of the work.

Let us assume that they have worked togetherly for N days.

So, we can write (N/20 + N/15)(A + B in N days) + 6/20(A alone in 6 days) = 1

or solving it we get N = 6.

That means A and B have worked togetherly for 6 days.