PS - Ratio Problem

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PS - Ratio Problem

by f2001290 » Wed Jun 13, 2007 8:52 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

OA is C.. I am having no clue about this.
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Re: PS - Ratio Problem

by gabriel » Wed Jun 13, 2007 9:17 am
f2001290 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

OA is C.. I am having no clue about this.
for every ratio there is a common factor between the 2 numbers ... i this case let it be "x" .. so the number of red cars and black cars are 3x and 8x respectively ..

given that the number of black cars= 72 = 8x ... therefore x = 9 .. so number of red cars = 3x=3*9 = 27 ... so answer should be D ..