A, B and C can do a piece of work in 11 days, 20 days and 55 days respectively, working alone. How soon can the work be done if A is assisted by B and C on alternate days?
Pick:  A) 7 days  B) 8 days  C) 9 days  D) 10 days  E) None of these
(A+B)'s 1 day's work=(1/11+1/20)=31/220;   (A+C)'s 1 day's work=(1/11+1/55)=6/55;   work done in 2 days=(31/220+6/55)=55/220=1/4   Now, 1/4 work is done by A in 2 days.   Whole work will be done in (2*4)= 
<gadget id="calculator">(2*4)</gadget>
<output>8</output>
8days.   Correct Option: 8 days
<result>B</result>
A, B and C can do a piece of work in 11 days, 20 days and 55 days respectively, working alone. How soon can the work be done if A is assisted by B and C on alternate days?