Proportions
Solve proportions and scale problems
lessons (3)
Solving Proportions
Learn to find unknown values in proportions using cross multiplication and other strategies.
Similar Figures
Learn what makes figures similar and how to use proportions to find missing measurements.
Scale Drawings
Learn how to read and create scale drawings using ratios and proportions.
Proportions are equations stating that two ratios are equal. Solving proportions using cross-multiplication is a fundamental skill used in scaling, map reading, cooking conversions, and countless real-world applications.
What Students Will Learn
- Set up proportions from word problems
- Solve proportions using cross-multiplication
- Identify when proportions apply
- Check solutions by verifying ratios are equal
- Apply proportions to real-world situations
Frequently Asked Questions
What is a proportion?
A proportion states that two ratios are equal: $\frac{a}{b} = \frac{c}{d}$. If you know three values, you can find the fourth.
How does cross-multiplication work?
For $\frac{a}{b} = \frac{c}{d}$, cross-multiply to get $ad = bc$. This creates an equation you can solve for the unknown.
When do I use proportions?
Use proportions when quantities change together at a constant rate: recipes, maps, similar figures, unit conversions, and scale models.