# Chapter 5: Applying Percents

**Basic**Created by: CK-12

## Introduction

Here you will learn all about percents and applications of percents. First, you will review how to convert between fractions, decimals, and percents. Then, you will learn how to find the percent of a number and use proportions to solve percent problems. You will also learn to solve real-world problems involving percents including discounts, sales tax, simple interest, and compound interest.

- 5.1.
## Recognize and Write Percents

- 5.2.
## Write Percents as Decimals

- 5.3.
## Write Percents as Fractions

- 5.4.
## Find the Percent of a Number

- 5.5.
## Use Proportions to Find Percents

- 5.6.
## Use Proportions to Solve Percent Problems

- 5.7.
## Use the Percent Equation to Find Part a

- 5.8.
## Use the Percent Equation to Find the Percent

- 5.9.
## Use the Percent Equation to Find the Base, b

- 5.10.
## Find the Percent of Increase

- 5.11.
## Find the Percent of Decrease

- 5.12.
## Find the Percent of Change

- 5.13.
## Find Retail Prices Given Wholesale, Markups and Sales Tax

- 5.14.
## Find Discount Prices Given Sales

- 5.15.
## Solve Statistics-Based Problems Involving Percents

- 5.16.
## Solve Percent Problems Involving Scientific Notation

- 5.17.
## Solve Real World Problems Involving Simple Interest

- 5.18.
## Solve Real World Problems Involving Compound Interest

### Chapter Summary

## Summary

You reviewed that percent means out of 100 and that percents can also be written as fractions or decimals. You learned how to solve problems involving percents including finding the percent of a number and finding what percent one number is of another number. To solve these problems you learned how to use the proportion \begin{align*}\frac{a}{b}=\frac{p}{100}\end{align*}. You also learned what is meant by a percent increase and a percent decrease and how to calculate these types of percents.

You then learned common applications of percents including discounts and sales tax. Other applications you studied were simple interest and compound interest. You learned the simple interest formula to calculate interest earned is \begin{align*}I=Prt\end{align*}. You learned the compound interest formula to calculate the future value of an account earning compound interest is \begin{align*}A=P(1+r)^t\end{align*}. In both formulas, \begin{align*}P\end{align*} is the principal, \begin{align*}r\end{align*} is the rate, and \begin{align*}t\end{align*} is the time. One important point to remember is that when working with compound interest, the way you calculate \begin{align*}r\end{align*} and \begin{align*}t\end{align*} changes depending on how often the interest is compounded.