SOLUTION: One semester the ratio of boys to girls in a class was 4 : 5 The next semester, one girl left the class and the ratio of boys to girls was then 6 : 7 How many boys were there in

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: One semester the ratio of boys to girls in a class was 4 : 5 The next semester, one girl left the class and the ratio of boys to girls was then 6 : 7 How many boys were there in       Log On


   



Question 875106: One semester the ratio of boys to girls in a class was 4 : 5
The next semester, one girl left the class and the ratio of boys to girls was then 6 : 7
How many boys were there in the class?
A.) 15
B.) 14
C.) 13
D.) 12
E.) 11

Answer by reviewermath(1029) About Me  (Show Source):
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Q:
One semester the ratio of boys to girls in a class was 4 : 5
The next semester, one girl left the class and the ratio of boys to girls was then 6 : 7
How many boys were there in the class?
A:
The number of boys is 4k and the number of girls is 5k.
So %284k%29%2F%285k+-+1%29+=+6%2F7, cross-multiply
30k - 6 = 28k
30k - 28k = 6
2k = 6, divide both sides by 2
k = 3
Therefore, 4k = 4(3) = 12 boys