7. A can do a piece of work in 14 days which B can do it in 21 days. They begin together but 3 days
before the completion of the work, A leaves off. Find the total number of days taken to finish work
(Ans: 8.5 days)
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Answer:
let A and B be x and y respectively
work done by A = 1/14
work done by B = 1/21
work done by both in 1 day = 1/14+1/21 = 5/42
work done in 3 days by both = 5/42×3 =15/42
as A has left
work done by B = 15/42÷1/21 =15/42×21 = 15/2
total days taken to complete = 5/42 + 15/2
= 5+315/42
= 320/42
= 7.6
I have tried my best dude
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