math
posted by allie on .
In a class of 80 seniors, there are 3 boys for every 5 girls. In the junior class, there are 3 boys for every 2 girls. If the two classes combined have an equal number of boys and girls, how many students are in the junior class?

If there are
3x senior boys and 5x senior girls
3y junior boys and 2y junior girls
3x+3y = 5x+2y
3x+5x = 80
so, x=10
and y=20
juniors have 60 boys and 40 girls.
seniors have 30 boys and 50 girls 
3+5=8
80/8=10
x=10 YES
b=30 YES
g=50 YES
y=10 NO
b=30 NO
g=20 NO
Because 60 doesn't = 70
y=20 YES
b=60 YES
g=40 YES
Because 90 = 90
S = 30 boys and 50 girls
J = 60 boys and 50 girls