A and B, working together can finish a piece of work in 6 days, while A alone can do it in 9 days. How much time will B alone take to finish it?
Number of days A required do a piece of work : 9 days
Let number of days B required do a piece of work : X days
Number of hours required by A and B together to do a piece of work : 6 days
Work done by A in one day: 
Work done by B in one day: 
Work done by A and B together in a day : 
Work done by A and B together in one day : 
= 
= 
⇒ 6X + 54 = 9X
⇒ 3X = 54
⇒ X = 54/3 = 18
B can do the work 18 days
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