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Ratio and Proportion

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Ratio and Proportion

by rintoo22 » Thu Mar 21, 2013 6:07 am
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 am getting an answer of 27 which is not correct. Kindly assist.
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by Anju@Gurome » Thu Mar 21, 2013 6:11 am
rintoo22 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?
Say, number of red and black cars are 3x and 8x, respectively.
So, 8x = 72 --> x = 9

Hence, 3x = 3*9 = 27

The correct answer is D.
Last edited by Anju@Gurome on Thu Mar 21, 2013 6:55 am, edited 1 time in total.
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by rintoo22 » Thu Mar 21, 2013 6:15 am
Exactly !!!. As much as I thought. But the answer posted in mock test is 24. After your response I am confirmed the 27 is rt. Thanks for the response.
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by Brent@GMATPrepNow » Thu Mar 21, 2013 6:15 am
rintoo22 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 am getting an answer of 27 which is not correct. Kindly assist.
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

Cheers,
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by Anju@Gurome » Thu Mar 21, 2013 6:58 am
rintoo22 wrote:But the answer posted in mock test is 24.
That's not possible as ratio of 24 to 72 is 1 to 3, not 3 to 8.
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by killerdrummer » Thu Mar 21, 2013 10:07 am
undoubtedly 27!! :)
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