Many people use the terms "ratio" and "proportion" as though they mean the same thing, but (red alert!) they do not mean the same thing.
For example, if you consider the number of boys and girls in your math class, a ratio would compare the number of girls to boys, while a proportion would compare the number of girls to the total number of students in your class.
Ratios can be written three different ways. If your town has vampires and werewolves, the ratio of vampires to werewolves can be written as:
You will notice that the last way looks a lot like a fraction. And, like a fraction, ratios and proportions can be reduced, exactly as you would reduce a fraction. By dividing both numbers by , the ratio can be written as: