SOLUTION: In a particular classroom there are 1.25 girls for every 2 boys. If this ratio is consistent across the school, how many boys are there in this school with a total student popul

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Question 966651: In a particular classroom there are 1.25 girls for every 2 boys.
If this ratio is consistent across the school, how many boys are there in this school with a total student population of 650?
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
let b = number of boys
let g = number of girls
b + g = 650

the ratio of girls to boys is equal to g/b which is equal to 1.25 / 2

in the ratio equation of g/b = 1.25 / 2, cross multiply to get 2 * g = 1.25 * b.

solve for g to get g = 1.25 * b / 2.

you are solving for g, because you want the original eqution of b + g = 650 to be in terms of b only.

this is accomplished by solving for g in terms of b and then using what g is equal to in terms of b rather than using g.

in the equation of b + g = 650, replace g with 1.25 * b / 2 to get:

b + g = 650 becomes b + 1.25 * b / 2 = 650

multiply both sides of this eqution by 2 to get:

2 * b + 1.25 * b = 650 * 2

combine like terms to get 3.25 * b = 650 * 2

simplify to get 3.25 * b = 1300.

divide both sides of this equation by 3.25 to get b = 1300 / 3.25 = 400.

that's your solution.

b = 400

you also get:

g = 650 - 400 = 250
b + g = 400 + 250 = 650