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# The ratio of boys to girls in a school is 9 to 11. After 36 more girls

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The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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18 Oct 2016, 02:12
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15% (low)

Question Stats:

85% (01:41) correct 15% (02:25) wrong based on 120 sessions

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The ratio of boys to girls in a school is 9 to 11. After 36 more girls join, the ratio becomes 9 to 13. How many boys are there in the school?

A. 102
B. 115
C. 132
D. 162
E. 234

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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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18 Oct 2016, 02:21
2
Bunuel wrote:
The ratio of boys to girls in a school is 9 to 11. After 36 more girls join, the ratio becomes 9 to 13. How many boys are there in the school?

A. 102
B. 115
C. 132
D. 162
E. 234

Boys : Girls
9 : 11

let the boys be 9x and the girls be 11x. Now, 36 more girls are added -------> 9:13(new ratio).

so,

9x/(11x+36) =9/13.

solving,

We get : x=18

so No. of boys in the school are :9x= 9*18= 162

hence (D)
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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18 Oct 2016, 02:27
Let x be ratio multiplier at first and y be the ratio multiplier after adding 36.

9y/13y=9x/11x+36

Equate numerator and denominator

9y=9x

y=x

13y=11x+36

13y-11y=36

y=18

Number of boys = 9*18 = 162

D

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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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18 Oct 2016, 02:52
Bunuel wrote:
The ratio of boys to girls in a school is 9 to 11. After 36 more girls join, the ratio becomes 9 to 13. How many boys are there in the school?

A. 102
B. 115
C. 132
D. 162
E. 234

Given B/G = 9/11 => B = 9G/11

Now 36 girls are added then ratio changes.

B/G+36 = 9/13. Now sub B value in this equation.

9G/11(G+36) = 9/13 => G = 198 and B = 162.

IMO option C.
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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18 Oct 2016, 09:03
2
2
Bunuel wrote:
The ratio of boys to girls in a school is 9 to 11. After 36 more girls join, the ratio becomes 9 to 13. How many boys are there in the school?

A. 102
B. 115
C. 132
D. 162
E. 234

13x - 11x = 36

So, 2x = 36

x = 18

So, No of boys is 9*18 =162

Similar Question : a-fresh-water-aquarium-contains-molly-fish-and-guppy-fish-at-a-ratio-227448.html
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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20 Oct 2016, 05:43
msk0657 wrote:
Bunuel wrote:
The ratio of boys to girls in a school is 9 to 11. After 36 more girls join, the ratio becomes 9 to 13. How many boys are there in the school?

A. 102
B. 115
C. 132
D. 162
E. 234

Given B/G = 9/11 => B = 9G/11

Now 36 girls are added then ratio changes.

B/G+36 = 9/13. Now sub B value in this equation.

9G/11(G+36) = 9/13 => G = 198 and B = 162.

IMO option C.

I think you meant D.
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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27 Oct 2016, 20:22
9x/(11x+36) = 9/13
117x=99x+324
18x=324
x=18

9x = 9(18) = 162
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls  [#permalink]

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09 Mar 2018, 19:48
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Re: The ratio of boys to girls in a school is 9 to 11. After 36 more girls   [#permalink] 09 Mar 2018, 19:48
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