There are 2 types of ratios: Part-to-Wholes, and Part-to-Part ratios.
Part-to-part ratios show the relationship between the two groups.
Lets say theres 10 fruits in a fruit bowl.
If you have 3 apples, and 7 oranges, then the ratio is 3:7 as the part-to-part ratio. But the part-to-whole ratio would be either 3:10 ( for apples) or 7:10 (for oranges)