7.13.A

Math7th Grade

The Standard

calculate the sales tax for a given purchase and calculate income tax for earned wages

Texas Essential Knowledge and Skills for Mathematics

Teacher's field guide

What Students Need to Do: Students convert a tax rate from a percent to a decimal and multiply it by the taxable amount. They find sales tax on a purchase and income tax on earned wages, then label the result as tax.
What Mastery Looks Like: Given a price or wage amount and a tax rate, a student chooses the correct base and calculates the tax accurately. The student shows the multiplication and distinguishes the tax amount from the total cost or take-home pay.
Common Misconceptions: Students often multiply by the whole-number percent, such as 8 instead of 0.08, or divide by 100 twice. They may report the purchase total instead of sales tax, subtract sales tax, or use hours worked instead of gross wages for income tax.
How to Assess It: Exit ticket: A game costs $36 and sales tax is 8.25%. Jordan earns $420 and pays 12% income tax. Find each tax amount and show the equation.

Lesson moves

Give pairs store ads, play money, and tax-rate cards. Students choose two items and calculate the sales tax for each purchase.
Ask students to explain why 7.5% becomes 0.075 and why the tax amount is smaller than the taxable purchase or wages.
Run a matching game with price or wage cards, tax-rate cards, equations, and tax amounts. Teams justify every match.
Use a sample pay stub and receipt to identify gross wages, taxable purchase amounts, rates, and the tax charged.

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