A ratio shows the relative sizes of two or more values.
Ratios can be shown in different ways. Using the ":" to separate example values, or as a single number by dividing one value by the total.
Example: if there is 1 boy and 3 girls you could write the ratio as:
1:3 (for every one boy there are 3 girls)
1/4 are boys and 3/4 are girls
0.25 are boys (by dividing 1 by 4)
25% are boys (0.25 as a percentage)