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A certain research group plans to create computer models...

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by gmattesttaker2 » Sun Aug 18, 2013 1:53 pm
Hello,

Can you please assist with this question? This is from MGMAT. Thanks for your help.


A certain research group plans to create computer models of x% of a list of 10,000 bacterial species known to inhabit the human body. After a budget cut, the group finds it must reduce this selection by (x − 5)%. In terms of x, how many species of bacteria will the group be able to model?

OA: [spoiler](x)(105 - x)[/spoiler]
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by Java_85 » Sun Aug 18, 2013 2:49 pm
I think the answer is 100x-500 , and don't think the OA is right. Please correct me if I'm wrong.
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by ganeshrkamath » Mon Aug 19, 2013 1:07 am
gmattesttaker2 wrote:Hello,

Can you please assist with this question? This is from MGMAT. Thanks for your help.


A certain research group plans to create computer models of x% of a list of 10,000 bacterial species known to inhabit the human body. After a budget cut, the group finds it must reduce this selection by (x − 5)%. In terms of x, how many species of bacteria will the group be able to model?

OA: [spoiler](x)(105 - x)[/spoiler]
Number of specied that the group plans to model = x% of 10000 = x/100 * 10000 = 100x
Reduce by (x-5)% :
Number of species that the group will be able to model = 100x * (100 - (x-5))/100
= [spoiler]x * (105 - x)
[/spoiler]

Take an example : x = 30
30% of 10000 = 3000
Reduce by 25% => 3000 * (100-25)/100
= 3000 * 75/100 = 2250

30*(105-30) = 30*75 = 2250

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by ganeshrkamath » Mon Aug 19, 2013 1:21 am
Java_85 wrote:I think the answer is 100x-500 , and don't think the OA is right. Please correct me if I'm wrong.
Please explain how you arrived at your answer.
I'm getting the same answer as the OA (see above).

Cheers
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by GMATGuruNY » Mon Aug 19, 2013 3:54 am
gmattesttaker2 wrote: A certain research group plans to create computer models of x% of a list of 10,000 bacterial species known to inhabit the human body. After a budget cut, the group finds it must reduce this selection by (x − 5)%. In terms of x, how many species of bacteria will the group be able to model?
Since the answer choices on the GMAT would all be IN TERMS OF A VARIABLE -- x -- we could PLUG IN.

Let x = 25.
Number of models before the budget cut = x% of 10,000 = 25% of 10,000 = 2500.
Percentage decrease after the budget cut = x-5 = 25-5 = 20%
Number of models after the 20% decrease = 2500 - .2(2500) = 2500-500 = 2000. This is our target.
Now we plug x=25 into the answers to see which yields our target of 2000.

Answer choice: (x)(105 - x) = 25(105-25) = 25(80) = 2000.
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by Java_85 » Mon Aug 19, 2013 8:15 am
ganeshrkamath wrote:
Java_85 wrote:I think the answer is 100x-500 , and don't think the OA is right. Please correct me if I'm wrong.
Please explain how you arrived at your answer.
I'm getting the same answer as the OA (see above).

Cheers
I was saying that (x/100)* 10000= 100x initial number of models
we're decreasing it to (x-5/100)*10000=> 100x-500 is the number of species we can model.
Which is also correct, but different
Last edited by Java_85 on Mon Aug 19, 2013 4:13 pm, edited 1 time in total.
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by gmattesttaker2 » Mon Aug 19, 2013 3:52 pm
GMATGuruNY wrote:
gmattesttaker2 wrote: A certain research group plans to create computer models of x% of a list of 10,000 bacterial species known to inhabit the human body. After a budget cut, the group finds it must reduce this selection by (x − 5)%. In terms of x, how many species of bacteria will the group be able to model?
Since the answer choices on the GMAT would all be IN TERMS OF A VARIABLE -- x -- we could PLUG IN.

Let x = 25.
Number of models before the budget cut = x% of 10,000 = 25% of 10,000 = 2500.
Percentage decrease after the budget cut = x-5 = 25-5 = 20%
Number of models after the 20% decrease = 2500 - .2(2500) = 2500-500 = 2000. This is our target.
Now we plug x=25 into the answers to see which yields our target of 2000.

Answer choice: (x)(105 - x) = 25(105-25) = 25(80) = 2000.
Hello Mitch,

Thank you very much for the excellent explanation.

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