1. A can do a piece of work in 10 days and B alone can do it in 15 days. How much time will both take to finish the work ?


This question can be solved by different methods. We need to conserve time in exams so solving this problem using equations is the good idea.


Time taken to finish the job = XY / (X + Y)

= 10 x 15 / (10 + 15)

= 150 / 25

= 6 days



2. A and B together can do a piece of work in 10 days. B alone can finish it in 20 days. In how many days can A alone finish the work ?


 Time taken by A to finish the work = XY/(Y-X)

= 10 x 20 / (20-10)

=  200/10

= 20 days




Key Words : Nobel Prize 2014, Kerala PSC, Secretariat Assistant