math
posted by Al on .
Class A has the same number of students as Class B. The ratio of the number of girls in Class A to the number of girls in Class B is 3 : 2. The ratio of the number of boys in Class A to the number of boys in Class B is 3 : 5. What is the ratio of the number of girls to boys in Class B?

Make a simple chart
....class A......class B
boys .. girls...boys .. girls
3y ...... 3x.......5y .... 2x
we know 3y+3x = 5y+2x
x = 2y
ration of girls to boys in class B
= 2x : 5y
= 2(2y) : 5y
= 4 : 5
There is no unique solution , just pick any value for y
e.g. using y = 5, then x = 10 (from x = 2y)
in the chart:
15.. 30....... 25 .. 20 satisfies the condition
y = 8, then x = 16
24 .. 48 ..... 40 .. 32 satisfies the condition
etc.