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? Select the correct option.
A) 9 days  B) 11 days  C) 8 days  D) 10 1/4 days  E) None of them
(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.   Answer is 10 1/4 days.
<result>D</result>
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?