## 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 \(d\)”.