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by MBA.Aspirant » Sat Aug 06, 2011 9:21 pm
A can complete a project in 20 days and B can complete the same project in 30 days. If A and B start working on the project together and A quits 10 days before the project is completed, in how many days will the project be completed?

(a) 18 days
(b) 27 days
(c) 26.67 days
(d) 16 days
(e) 20 days
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by Anurag@Gurome » Sat Aug 06, 2011 9:27 pm
MBA.Aspirant wrote:A can complete a project in 20 days and B can complete the same project in 30 days. If A and B start working on the project together and A quits 10 days before the project is completed, in how many days will the project be completed?
As A quits 10 days before the project is completed, B is working for the last 10 days. Hence, in last 10 days B will finish 1/3 of the project.

Therefore, A and B together has completed 2/3 of the project.

Now, A and B together completes (1/20 + 1/30) = 5/60 = 1/12 of the project in one day.
Hence, they will complete 2/3 of the project in 12*(2/3) = 8 days.

Therefore, the project will be completed in (8 + 10) = 18 days.

The correct answer is A.
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by GMATGuruNY » Sat Aug 06, 2011 11:37 pm
I posted a solution here:

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