A and B can together complete a task in 18 hours. After 6 hours A leaves. B takes 36 hours to finish rest of the task. How many hours would A have taken to do the task if he worked alone?
Let the total number of units of work =108
A and B can do in 18 hours so 108/18 =6 units
each hour they both can do 6 units
For 6 hours they both worked and so 36 units is done so 108-36=72 units of work is done by B alone in 36 hours
I.e 72/36 = 2 units per dayÂ
Therefore a+b=6
a=6-2
a=4 units per day
If A worked alone then 108/4 =27 hours  Â
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