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Explain…
Ratio and Proportion

Explain…Ratio and Proportion
A ratio is a comparison of two numbers. For example, if 25 students -- 10 boys and 15 girls -- are in your class, then the ratio of boys to girls is 10 to 15. A ratio can be expressed in three ways. The ratio of boys to girls in your class might be expressed as

• 10 to 15
• 10:15
• 10/15.

A proportion is a statement (or equation) that says two ratios are equal. A proportion can be expressed in two ways:

• 10:15 = 2:3
• 10/15 = 2/3

An important fact to know about proportions, is that if one of the numbers in a proportion is not known, cross multiplying can be used to find the unknown number. For example, cross multiply to find the missing number in the proportion below:
? 2 2 x 15 = 30 -- = -- 15 3 3 x ? = 30 The missing number, therefore, is 10.

Ratio Lesson Plans

• Learning About Ratios
• Learning ratios and proportions through scale drawings
• Math is Fun
• Ratio
• Ratio, Sweet Ratio

Ratio Worksheets

• EdHelper.com
• Homework for Kids
• Ratio Worksheet
• Ratios and Proportions
• Ratio and Proportion Recipes

Ratio Interactive Activities

• All About Ratios
• Interactive Worksheets
• Practice with Ratios
• Ratio and Proportion Activity
• Using Proportions

Article by Linda Starr
Education World®
Copyright © 2007 Education World

03/09/2007