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Ratio and Proportion


 

ExplainRatio 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.

More Ratio Resources

* AAA Math
* Algebra Help
* BBC Skillwise
* Get Help with Ratios
* Math.com
* Purple Math

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

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Ratio Interactive Activities


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