What is a ratio?
A ratio has two or more numbers that symbolize relation to each other. Ratios are used to compare numbers, and you can compare them using division.
If the ratio is 5: 3, (girls: boys) we can use this equation to figure out how many boys there are if there are 35 girls:
Why do we multiply by 0.6?
We can see that in the ratio 5: 3, 5 is being multiplied by 0.6 to get three. If the relationship between the numbers 5 and 35 stays proportional, we multiply 35 by 0.6.
Therefore, the ratio of girls to boys is 35: 21, meaning there are 21 boys.