Ratios are pairs of numbers and they are used to make comparisons.

A ratio compares two numbers using a fraction. Ratios can be written

three different ways:

(1) 2 to 3

(2) 2:3

(3) 2/3

They all mean the same thing. Pretend I have a class of 25 students:

10 students are boys and 15 are girls. I can compare number of boys

to girls using the ratio 10/15 (or 10:15; or 10 to 15). This ratio

means the same thing as saying that for every ten boys in my class, I

have 15 girls. You can "reduce" this fraction (remember, ratios are

comparisons using fractions) to 2/3 by dividing both numerator and

denominator by 5.

2/3 is a *ratio*.

A *ratio* says how much of one thing there is compared to another thing.