Unit 4, Lesson 10
Tax and Tip
Grade 7
Preparation
Lesson Narrative
In this lesson, students are introduced to two common applications of percent increase: sales tax and tips. Students can use any representation they would like to make sense of the situations. The tables presented in this lesson provide an opportunity for students to be more efficient by using an equation of the form . By repeatedly calculating the tax for different prices and then generalizing the process, they are engaging in expressing regularity in repeated reasoning (MP8).
There is an optional activity in which the tax rate is fractional, and the given dollar amounts are rounded to the nearest cent. This provides an opportunity for students to practice finding the constant of proportionality when rounding error makes it look like the relationship is not exactly proportional.
- Comprehend “sales tax” and “tip” as two contexts that involve adding a percentage of the initial amount.
- Explain (orally) how to calculate the total cost including a tax or tip, given the “subtotal” and the percentage.
- Explain (orally) how to determine the percentage of the subtotal that a tax or tip is.
Let’s learn about sales tax and tips.
Required Materials
Activity 2
Activity 3
Activity 4
Required Preparation
It is recommended that students be provided access to four-function calculators so that they can focus on reasoning about how numbers are related to each other, representing those relationships, and deciding which operations are appropriate (rather than focusing on computation).