Question

And b can do a piece of work in 35 and 30 days a respectively. they began to work together, but a left after some days and b finished the remaining work ir 20 days. after how many days did a leave?

Answer 1

One day work of A=1/35
one day work ofB=1/30
B's work in 20 days= 1/30*20 =2/3
So work done by both of them together=1 - 2/3=1/3
In one day both of them work= 1/30+1/35 = 1/30
Let 1/3 work will be done in x days
So, 1/3=1/30x
= 1/3*30=x
10= x
So 10 days A worked.