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A certain research group plans to create computer models of [#permalink]
09 Sep 2013, 09:59

1

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00:00

A

B

C

D

E

Difficulty:

65% (hard)

Question Stats:

50% (02:32) correct
50% (01:37) wrong based on 211 sessions

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?

A. x*x – 5x B. (x)(105 – x) C. (100)(105 – x) D. (100)(95 – x) E. (x-5)/100

Re: A certain research group plans to create computer models of [#permalink]
09 Sep 2013, 12:35

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

Initial: (x/100)*10000 = 100x (bacterial species) After reduce BY (x - 5)%, the percentage of bacterial species = 1 - (x - 5)% = 1 - (x - 5)/100 = (105 - x)/100 Note: Difference between "reduce to" [means: the remain] and "reduce by" [means: the remain = 1 - "reduce by"] So, the number of bacterial species after reducing: 100x*(105 - x)/100 = (x)*(105 - x) Ans is B.

Re: A certain research group plans to create computer models of [#permalink]
09 Sep 2013, 16:20

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

I believe the OA may be wrong. I got:

x% of 10000 is: \frac{x}{100}(10,000) = 100x

The reduced percentage can be stated as follows: (1 - \frac{x-5}{100})=(\frac{105-x}{100})

Multiplying the selection by the reduced percentage: 100x(\frac{105-x}{100})=x(105-x)

B _________________

If my post has contributed to your learning or teaching in any way, feel free to hit the kudos button ^_^

Re: A certain research group plans to create computer models of [#permalink]
09 Sep 2013, 17:38

I think OA is wrong too, but i got D.

out of 10,000 samples, 10,000(x-5)% will be studied. If x was originally 50%, that means 5,000 would have been studied. now at 50%-5%, 4,500 will be studied.

Re: A certain research group plans to create computer models of [#permalink]
11 Oct 2013, 01:37

2

This post received KUDOS

Expert's post

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

The number of species that the group plans to model = 10,000*\frac{x}{100} = 100x.

After a budget cut, the group finds it must reduce this selection by (x − 5)%, thus the group will be able to model 100x*(1-\frac{x-5}{100})=x(105-x).

Re: A certain research group plans to create computer models of [#permalink]
11 Oct 2013, 04:15

Bunuel wrote:

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

The number of species that the group plans to model = 10,000*\frac{x}{100} = 100x.

After a budget cut, the group finds it must reduce this selection by (x − 5)%, thus the group will be able to model 100x*(1-\frac{x-5}{100})=x(105-x).

Re: A certain research group plans to create computer models of [#permalink]
10 Jan 2014, 06:14

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

Use smart numbers.

OK lets say x = 50

So then 50% of 10,000 = 5000 Now after budget cut = 5000*45/100 = (50)(45)

Re: A certain research group plans to create computer models of [#permalink]
20 Jul 2014, 04:43

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?

A. \frac{x-5}{100} B. x^2 – 5x C. (x)(105 – x) D. (100)(105 – x) E. (100)(95 – x) _________________

“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”

Re: A certain research group plans to create computer models of [#permalink]
20 Jul 2014, 04:46

1

This post received KUDOS

Expert's post

WoundedTiger 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?

A. \frac{x-5}{100} B. x^2 – 5x C. (x)(105 – x) D. (100)(105 – x) E. (100)(95 – x)

Merging topics.

Please refer to the discussion above. _________________

Re: A certain research group plans to create computer models of [#permalink]
22 Jul 2014, 12:13

Bunuel wrote:

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

The number of species that the group plans to model = 10,000*\frac{x}{100} = 100x.

After a budget cut, the group finds it must reduce this selection by (x − 5)%, thus the group will be able to model 100x*(1-\frac{x-5}{100})=x(105-x).

Answer: B.

Hope it's clear.

Hi why you wrote 1- (x-5)% in the last step? could not understand the step.

Re: A certain research group plans to create computer models of [#permalink]
22 Jul 2014, 22:57

GGMAT760 wrote:

Bunuel wrote:

suyash23n 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?

a) x*x – 5x b) (x)(105 – x) c) (100)(105 – x) d) (100)(95 – x) e) (x-5)/100

The number of species that the group plans to model = 10,000*\frac{x}{100} = 100x.

After a budget cut, the group finds it must reduce this selection by (x − 5)%, thus the group will be able to model 100x*(1-\frac{x-5}{100})=x(105-x).

Answer: B.

Hope it's clear.

Hi why you wrote 1- (x-5)% in the last step? could not understand the step.

Thanks in advance

Actually its a reduction of (x-5)%; so written in that way

A certain research group plans to create computer models of [#permalink]
10 Aug 2014, 18:22

Based on the answer choices and the question, this question begs the use of x=5 as a sample number. Initial = 5%*10000 = 500 Reduction = 5-5=0%, so no math required here to calculate the reduction; just make sure that you can calculate 500 in your answer.

A. x*x – 5x = 0; No B. (x)(105 – x) = 500; Winner! C. (100)(105 – x) > 500; No D. (100)(95 – x) > 500; No E. (x-5)/100 = 0; No

B

I was a strong believer in using algebra for percent problems, but after missing 95% of them because of some careless error, I was converted to the sample number method. Generally speaking, picking smart numbers for percent problems will get you the correct answer more quickly and with the least errors.

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