Question

A and b can complete a work in 15 days and 10 days respectively. They started doing the work together but after 2 days b had to leave and a alone completed the remaining work. The whole work was completed in:

Answer 1

Let total work be 30 units (LCM of 10 and 15).

In one day, A can do 2 units of work and B can do 3 units of work.

In one day, both A and B can do 5 units of work.

In two days, A and B will complete 10 units of work. Remaining 20 units can be completed by A in 10 days (at rate of 2 units per day).

Hence, whole work will be completed in 12 days.

Answer 2

Only two cases arises in this:-

One is that the whole work would be completed in 15 days and second is that the whole work would be completed in 21 days.