Question

A and B working separately can do a piece of work in 9 and 12 days respectively, If they work for a day alternately, A beginning, in how many days, the work will be completed?

Answer 1

(A + B)'s 2 days' work =(1/9+1/12)=7/36 

Work done in 5 pairs of days =(5*7/36)=35/36  

Remaining work =(1-35/36)=1/36 

On 11th day, it is A’s turn. 1/9 work is done by him in 1 day. 

1/36 work is done by him in(9*1/36)=1/4 day

Total time taken = (10 + 1/4) days = 10 1/4days.