PS - Ratio Problem

[f2001290]

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.

[gabriel]

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 ..