# Chapter 4: Applying Proportions

**Basic**Created by: CK-12

## Introduction

Here you will learn all about ratios and proportions. You will start by learning what a ratio is and the different ways you can write a ratio. Next, you will learn about proportions and how to solve proportional equations. You will also learn how to solve real-world problems by writing and solving proportional equations. Finally, you will learn how to convert units of measurement using proportions.

- 4.1.
## Write, Compare, and Order Ratios

- 4.2.
## Use Unit Rates and Equivalent Rates

- 4.3.
## Write and Solve Proportions by Using Equivalent Rates

- 4.4.
## Write and Solve Proportions by Using Cross-Products

- 4.5.
## Connect Proportions to Real-World Situations

- 4.6.
## Use Unit Scale When Problem Solving

- 4.7.
## Use Scale Factor When Problem Solving

- 4.8.
## Read and Interpret Scale Drawings and Floor Plans

- 4.9.
## Read and Interpret Maps Involving Distance and Area

- 4.10.
## Understand Three-Dimensional Scale Models and Designs

- 4.11.
## Understand Scale Relationships

- 4.12.
## Convert Customary Units of Measurement

- 4.13.
## Convert Customary Units of Measurement in Real-World Situations

- 4.14.
## Convert Metric Units of Measurement

- 4.15.
## Convert Metric Units of Measurement in Real-World Situations

- 4.16.
## Use Metric and Customary Units of Measurement in Problem Solving

- 4.17.
## Solve Problems Involving Rates and Unit Analysis

### Chapter Summary

## Summary

You learned that a ratio is a comparison between two quantities and can be written in three ways. Just like fractions, two ratios can be equivalent and you can write ratios in lowest terms. You learned that when two ratios are equivalent, a proportion is formed.

You learned that you can use proportions to solve problems when you know that a common ratio exists between two quantities. Proportions that contain a variable can be solved by cross multiplying or by using equivalent rates. Typical problems that be solved using proportions are problems that have to do with scale drawings, scale models, or maps. You learned that you can also use proportions to convert between customary or metric units because a defined ratio exists between two given units. You practiced converting between different customary units, between different metric units, and between customary and metric units. You also learned how to solve problems involving rates and unit analysis.