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Mathematics » Introducing Percents » Solve Proportions and their Applications

# Key Concepts

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## Key Concepts

• Proportion
• A proportion is an equation of the form $$\frac{a}{b}=\frac{c}{d}$$, where $$b\ne 0$$, $$d\ne 0$$.The proportion states two ratios or rates are equal. The proportion is read “$$a$$ is to $$b$$, as $$c$$ is to $$d$$”.
• Cross Products of a Proportion
• For any proportion of the form $$\frac{a}{b}=\frac{c}{d}$$, where $$b\ne 0$$, its cross products are equal: $$a\cdot d=b\cdot c$$.
• Percent Proportion
• The amount is to the base as the percent is to 100. $$\frac{\text{amount}}{\text{base}}=\frac{\text{percent}}{100}$$

## Glossary

### proportion

A proportion is an equation of the form $$\frac{a}{b}=\frac{c}{d}$$, where $$b\ne 0$$, $$d\ne 0$$.The proportion states two ratios or rates are equal. The proportion is read “$$a$$ is to $$b$$, as $$c$$ is to $$d$$”.