Question

a and b can do piece work in 15 days and b can do piece of that work in 20 days. than a can do the work in how many day​

Answer 1

Answer:

A and B together complete a work in 15 days. A alone can do it in 20 days. In how many days B alone can do it?

A alone can do it in 20 days, means that he does (1/20)th part of the work in one day.

A and B together complete the work in 15 days, means that they do (1/15)th part of the work in one day.

Thus B does (1/15)-(1/20) part of the work in one day, i.e. (20–15)/(15*20) = 5/(15*20) = (1/60)th part of the work in one day. Or he can do the work in 60 days, working alone.

Check: A does (1/20)th part of the work in one day. B does (1/60)th part of the work in one day. A and B together do (1/20)+(1/60)th part of the work in one day, or (3+1)/60 = 4/60 or 1/15th part of the work in one day. Or they will complete the work in 15 days.