Expert: Lynn Houston - 2/5/2010

Question
If a computer teacher has 20 students, 8 of whom are women and 12 of whom are men. If her afternoon class has 30 students, how many of them must be women so that both classes have the same ratio of women to men?

Answer
let x = women and y = men

8/12 = x/y

x+y = 30
x = 30-y substitute the value of x into the first eq

8/12 = (30-y)/y  multiply both sides by 12y

8y = 12(30-y)  multiply
8y = 360 - 12y  add 12y to both sides
20y = 360  divide both sides by 20
y = 18, therefore x = 12  so 12 must be woman