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Machines-work problem

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by hpgmat » Sat Oct 24, 2009 3:06 pm
six machines , each working at the same constant rate, together can complete a certain Job in 12 days. How many Additional machines, each working at the same constant rate will be needed to complete the Job in 8 days?

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please show calc
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Re: Machines-work problem

by Brent@GMATPrepNow » Sat Oct 24, 2009 3:27 pm
hpgmat wrote:six machines , each working at the same constant rate, together can complete a certain Job in 12 days. How many Additional machines, each working at the same constant rate will be needed to complete the Job in 8 days?
2
3
4
6
8
please show calc
If 6 machines take 12 days to complete the job, then we can say that the job takes 72 "machine days" to complete the job (6x12=72)

To complete the job in 8 days would require 9 machines (72 machine days divided by 8)

So, we need an additional 3 machines. B
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