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The ratio of the number of red cars in a certain parking lot

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The ratio of the number of red cars in a certain parking lot  [#permalink]

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New post Updated on: 12 Jan 2014, 06:02
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The ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. If there are 72 black cars in the lot, how many red cars are there in the lot?

A. 11
B. 15
C. 24
D. 27
E. 32

I arrivied at answer D, but OA is diff. Please explain where is the trap?

Originally posted by udaymathapati on 26 Sep 2010, 11:34.
Last edited by Bunuel on 12 Jan 2014, 06:02, edited 1 time in total.
Edited the OA.
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Re: Black-red Car  [#permalink]

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New post 26 Sep 2010, 11:36
udaymathapati wrote:
The ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. If there are 72 black cars in the lot, how many red cars are there in the lot?
A. 11
B. 15
C. 24
D. 27
E. 32

I arrivied at answer D, but OA is diff. Please explain where is the trap?


\(\frac{red}{black}=\frac{3x}{8x}\) --> \(black=8x=72\) --> \(x=9\) --> \(red=3x=27\).

Answer: D (C is not correct).

Moreover if \(red=24\) then \(\frac{red}{black}=\frac{24}{72}=\frac{3}{9}\) and not \(\frac{3}{8}\).

Hope it helps.
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Re: Black-red Car  [#permalink]

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New post 26 Sep 2010, 20:04
D is correct

R/B = 3/8 and B =72
R = 72*3/8 = 27
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Re: The ratio of the number of red cars in a certain parking lot  [#permalink]

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New post 12 Jan 2014, 10:56
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Simply put

\(\frac{3}{8}\) = \(\frac{X}{72}\)

Cross Multiply so that

\(216=8x\)

x=27
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Re: The ratio of the number of red cars in a certain parking lot  [#permalink]

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New post 22 Dec 2015, 01:41
udaymathapati wrote:
The ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. If there are 72 black cars in the lot, how many red cars are there in the lot?

A. 11
B. 15
C. 24
D. 27
E. 32

I arrivied at answer D, but OA is diff. Please explain where is the trap?


Black car which is represented by 8 in ratio has actual value = 72 ----- (i.e. 8 x9)

Therefore, Red car which is represented by 3 in ratio will have actual value = 3x9 = 27 ----- (i.e. 3 x9)

Answer: Option D
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Re: The ratio of the number of red cars in a certain parking lot  [#permalink]

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New post 13 Jan 2018, 10:14
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udaymathapati wrote:
The ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. If there are 72 black cars in the lot, how many red cars are there in the lot?

A. 11
B. 15
C. 24
D. 27
E. 32


We can use equivalent ratios here
red/black: 3/8 = x/72
Cross multiply to get: 8x = (3)(72)
Divide both sides by 8 to get: x = (3)(9)
x = 27

Answer: D

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Re: The ratio of the number of red cars in a certain parking lot   [#permalink] 13 Jan 2018, 10:14
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