Working alone at their respective constant rates, A can complete a task in ‘a’ days and B in ‘b’ days. They take turns in doing the task with each working 3 days at a time. If A starts they finish the task in exactly 9 days. If B starts, they take a day more. How long does it take to complete the task if they both work together? Pick one:	A) 8	B) 6	C) 4	D) 5	E) 9/2
Work done by AB in a day = xy respectively.   When A starts:   No. of days when A works = 6No. of days when B works = 3 → 6x + 3y = 1   When B starts:   No. of days when A works = 4 No. of days when A works = 5 → 5x + 4y = 1   Solving the above two equations for xy   x = 1/9 y = 1/9   → Total work done by AB in a day = 1/9 + 1/9 = 2/9   → No. of days to complete the work when both work together = 9/2;   Answer: 9/2
<result>E</result>
Working alone at their respective constant rates, A can complete a task in ‘a’ days and B in ‘b’ days. They take turns in doing the task with each working 3 days at a time. If A starts they finish the task in exactly 9 days. If B starts, they take a day more. How long does it take to complete the task if they both work together?