If a and b together can complete a piece of work in 15 days and b alone in 20 days . In how many days a alone can complete the work?

Solution (By Examveda Team)

 a and b can complete the work in 15 days.
Percentage of work done by a and b in one day = 100/15 = 6.66%.

b alone can complete the whole work in 20 days.

So, percentage of work done by b in one day = 100/20 = 5%.
Percentage of work done by a in one day = 6.66 - 5 = 1.66%.

Thus, a can complete the whole work alone in = 100/1.66 = 60 days. (Approx.).

Alternatively,

 a and b can complete the work in = 15 days.

Part of work done by a and b in one day = 1/15.

b can complete the work alone in = 20 days.

So, part of work done by b in one day = 1/20.

Part of work done by a = 1/15 - 1/20 = 1/60

a can complete the work in = 1/ (1/60) = 60 days.