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If a pre-school admits 15 additional boys to its current

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If a pre-school admits 15 additional boys to its current  [#permalink]

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New post 18 May 2012, 11:16
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In the process of building my foundation, and I am complete stuck on this question.

If a pre-school admits 15 additional boys to its current population, the percentage of girls will be 40%. If currently the number of boys equals the number of girls, how many total students are currently enrolled in the school?

A. 30
B. 40
C. 60
D. 90
E. 120

I've seen the explanation, which leads you to the equations (b + 15)/(g + b + 15) = 3/5, g=b.

I don't understand why you would use g + b + 15 if you are searching for the current enrollment and why you would have b + 15/ g + b + 15. Is there any easier way to approach this question?

If someone can break this down for me, I'd REALLY appreciate it. Thanks!

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Re: If a pre-school admits 15 additional boys to its current  [#permalink]

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New post 18 May 2012, 13:46
Vixen wrote:
In the process of building my foundation, and I am complete stuck on this question.

If a pre-school admits 15 additional boys to its current population, the percentage of girls will be 40%. If currently the number of boys equals the number of girls, how many total students are currently enrolled in the school?

A. 30
B. 40
C. 60
D. 90
E. 120

I've seen the explanation, which leads you to the equations (b + 15)/(g + b + 15) = 3/5, g=b.

I don't understand why you would use g + b + 15 if you are searching for the current enrollment and why you would have b + 15/ g + b + 15. Is there any easier way to approach this question?

If someone can break this down for me, I'd REALLY appreciate it. Thanks!


Say currently there are \(g\) girls and \(b\) boys.

After 15 boys are admitted the number of boys would become \(b+15\) and the total number of students \(g+(b+15)\). We are told that the number of girls compose 40% of that number, so \(0.4(g+b+15)=g\).

Now, since we are also told that currently the number of boys equals the number of girls (g=b) then when substituting \(b\) by \(g\) we get: \(0.4(g+g+15)=g\) --> \(g=30\) --> total=g+b=2g=60.

Answer: C.

Hope it's clear.
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Re: If a pre-school admits 15 additional boys to its current  [#permalink]

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New post 16 Jan 2019, 05:59
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Re: If a pre-school admits 15 additional boys to its current   [#permalink] 16 Jan 2019, 05:59
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