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GMAT Prep - Work Rate Problem

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GMAT Prep - Work Rate Problem

by bubbliiiiiiii » Tue Aug 09, 2011 9:11 pm
Though I have arrived at the correct answer, I would like to know how to approach this problem. This is one of my weak areas in problem solving. Experts please help.

My approach:

One day job of six machines = 1/(12*6)

One day job of six + x machines = 1/[(6+x)*8] where x is the number of additional machines needed.

I equated the two equations above,

1/72=1/(48 + 8x)

48+8x = 72 => x=3.

Would be glad to know other approaches as well.
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by krishna8143 » Tue Aug 09, 2011 9:20 pm
the question is not complete
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by Anurag@Gurome » Tue Aug 09, 2011 9:23 pm
bubbliiiiiiii wrote:Though I have arrived at the correct answer, I would like to know how to approach this problem. This is one of my weak areas in problem solving. Experts please help.

My approach:

One day job of six machines = 1/(12*6)

One day job of six + x machines = 1/[(6+x)*8] where x is the number of additional machines needed.

I equated the two equations above,

1/72=1/(48 + 8x)

48+8x = 72 => x=3.

Would be glad to know other approaches as well.
Let x machines are needed to complete the job in 8 days.
Machines...Days
6... 12
x ... 8

Please note here that more machines would complete a job in fewer number of days, so there will an inverse relationship.

6 * 12 = x * 8
x = 9 implies no. of additional machines required = 9 - 6 = 3

The correct answer is B.
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GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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