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Proportion Basics

A proportion is a special form of an algebra equation. It is used to compare two ratios or make equivalent fractions. A ratio is a comparison between two values. Such as the following:

1 apple: 3 oranges

This ratio compares apples to oranges. It means for every apple there are 3 oranges.

A proportion will help you solve problems like the one below.

Jane has a box of apples and oranges in the ratio of 2:3. If she has six apples, how many oranges does she have?

Before we begin to set up proportions for a word problem, we will concentrate on solving proportions. Remember, a proportion is a comparison between two ratios. The proportion shown below compares two ratios which are in the fraction form.

1   x
- = -
2   6

The four parts of the proportion are separated into two groups, the means and the extremes, based on their arrangement in the proportion. Reading from left-to-right and top-to-bottom, the extremes are the very first number, and the very last number. This can be remembered because they are at the extreme beginning and the extreme end. Reading from left-to-right and top-to-bottom, the means are the second and third numbers. Remembering that "mean" is a type of average may help you remember that the means of a proportion are "in the middle" when reading left-to-right, top-to-bottom. Both the means and the extremes are illustrated below.

Proceed to the next page to learn how to use the means and extremes to solve a proportion.


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