Key Concepts

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

Glossary

proportion

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