📚 Practice With Worksheets

Use these worksheets to review percent equations, percent change, markup, markdown, percent error, sales tax, and simple interest.

▶️ Learn With Videos

Review how to calculate a total bill after tax, find percent change, and solve markup word problems.

🛠️ How to Use This Tool

Read the situation and try to solve it before using the equation setup.

If you need help getting started, click Show Setup, enter the values from the problem, and click Check Equation. The setup card and sound feedback will show whether the equation is correct.

Enter your final answer and click Check Answer. After one answer attempt, the worked solution unlocks.

Use Show Work and Hide Work to study the general formula, substitution, computation, and final answer.

🧠 Things to Notice

Many percent equations are built from the same idea: part equals percent times whole.

For percent change, markup, and markdown, compare the change to the original value.

The optional setup helps translate words into algebra, while the locked worked solution encourages an honest attempt first.

📘 Vocabulary

Percent Equation: An equation used to solve a percent problem.

Percent: A rate or ratio that means “out of 100.”

Part: The amount being compared to the whole.

Whole: The total amount, original amount, or base amount.

Percent Change: The percent increase or decrease from an old value to a new value.

Markup: An increase from a wholesale or original cost to a higher selling price.

Markdown: A decrease from an original price to a lower sale price.

Percent Error: A percent that compares the absolute error to the actual value.

Sales Tax: An added percent of the price before tax.

Principal: The starting amount of money in a simple interest problem.

Interest: The amount of money earned or charged over time.

Interest Rate: The percent rate used in a simple interest equation.

📐 Percent Equation Rules

Basic Percent:

\(\displaystyle \text{part}=(\text{percent as decimal})(\text{whole})\)

Percent Change, Markup, and Markdown:

\(\displaystyle \text{percent change}=\frac{\text{new}-\text{old}}{\text{old}}\times 100\%\)

Find the Percent:

\(\displaystyle \text{percent}=\frac{\text{part}}{\text{whole}}\times 100\%\)

Percent Error:

\(\displaystyle \text{percent error}=\frac{|\text{predicted}-\text{actual}|}{\text{actual}}\times 100\%\)

Find the Whole:

\(\displaystyle \text{whole}=\frac{\text{part}}{\text{percent as decimal}}\)

Sales Tax:

\(\displaystyle \text{tax}=(\text{tax rate as decimal})(\text{price before tax})\)

Simple Interest:

\(\displaystyle I=PRT\)

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