The ratio is the comparison of two or more quantities. For example, the no. of books is 5 & the no. of notebooks is 10. So the ratio of books to notebooks is 5:10 or 1:2. Means the quantity of notebooks is two times of books.

When two or more ratios are equal to each other, so they are called Proportion. For example, In Class A the ratio of no. of girls to the no. of boys is 2:3 & In Class B the ratio of no. of girls to the no. of boys is 2:3. So both ratios are in proportion because they are equal.