Chapter 12

Ratios and Proportions

A ratio is a comparison between two numbers. A proportion is a simple and useful equation based on a ratio. Ratios and proportions are closely related to fractions. In most cases, changing a ratio into a fraction will help you apply your knowledge of fractions to solve the problem you’re facing.

The Problems You’ll Work On

The following are a few examples of the types of problems you face in this chapter:

Knowing how ratios and fractions are related

Using ratios to set up a proportional equation

Solving word problems using proportions

What to Watch Out For

Here are a few tips for sorting out problems that involve ratios and proportions:

Ratios are easier to work with as fractions. Change a ratio to a fraction by putting the first number in the numerator and the second number in the denominator. For example, the ratio 2:5 is equivalent to the fraction .

A proportion is an equation that includes two ratios set equal to each other. For example: