# A and B can do it piece of work in 14 days and 21 days respectively. They start work together but 3days before completely work A leave it. In How many days work will be finish?

2
by Neelam27
(A+B) 1 day work =1/14+1/21=5/42 now, 3 days work 3*5/42,now remaining work =1-15/42=42-15/42=17/42 so b I day work =1/21 hence remaining days =21*17/42=17/2 now total no of days= 3+17/2=so final answer is 23/2 days i.e 11.5 days only
thx to all

2014-07-25T09:26:20+05:30

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Suppose A & B together could do work in n days, (n = 8.4).
A left after n-3 days, ie., 5.4 days.
Work left by A is 3/14.
B can do that in 4.5 days.
Total Time is n-3 days + 4.5 = 12.9.

2014-07-26T14:51:09+05:30

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
In 1 day (A+B) can do work = 1/14 + 1/21  = 5/42
Now, 3 days before Completion the work remaining is = 3 days work = 3 * 5/42 = 5 / 14.  This is the work remained when A left the project.
So 1 -  5/14 = 9/ 14 work was done by A & B together.  The time taken for that would be :  (9/14) / (5/42)  = 27 / 5 days = 5.4 days

Now the remaining work 5/14 is done by B alone.
1 day work by B = 1/21
B took (5 /14)  / (1/21) = 15/2 = 7.5 days
Total time to complete project is  5.4 + 7.5  = 12.9 days