Question

A and B together can do a piece of work in 12 days. If A alone can finish the same work in 20 days, in how many days B alone can finish the same work

Answer 1

Let time taken by A alone be x days
and, time taken by B be y days

we are given, 1/x+1/y=1/12
                       but 1/x=1/20

                      so, 1/y=1/12-1/20
                            1/y=   5-3/60
                            1/y=2/60
                             so, y =30
 so B can Finish the work alone in 30 days