Ratios and proportions are ways to compare numbers and show relationships between quantities. They’re used all the time in real life—recipes, maps, shopping, speed, and more.
Ratios
A ratio compares two quantities by showing how many times one quantity is compared to another.
Ways to Write a Ratio
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Using a colon:3 : 4
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As a fraction: 3/4
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Using words: 3 to 4
All three mean the same thing.
Example of a Ratio
If there are 3 apples and 4 oranges, the ratio of apples to oranges is:
3 : 4
Simplifying Ratios
Just like fractions, ratios can be simplified.
Example:
6:8 = 3:4
(Divide both numbers by 2)
Proportions
A proportion is an equation that says two ratios are equal.
Example of a Proportion
2/3 = 4/6
Both ratios represent the same comparison, so this is a true proportion.
Solving Proportions
To solve proportions, we often use cross multiplication.
Example
x/5 = 6/10
Cross multiply:
10x = 3
x = 3
Key Differences
| Ratios | Proportions |
|---|---|
| Compare two quantities | Show two ratios are equal |
| Written as 3:4 or 3/4 | Written as an equation |
| Can be simplified | Can be solved for a variable |
Real-Life Examples
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Recipes: 2 cups of flour for every 1 cup of sugar
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Maps: Scale shows distance
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Shopping: Unit prices
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Speed: Miles per hour