Lesson objective: Solve real-world, multi-step problems involving percent change by writing equations.

This lesson provides an opportunity for students to apply their knowledge and understanding of percent change to a real-life situation. Students are asked to calculate percent change through discounts and sales tax, as well as determining the final cost to the buyer. Students will then calculate the monthly payment to select the product with the lower price.

Key Concept students will use:

Skills students will use:

- calculate percent increase or decrease by setting up an equation to represent the situation and solving for the missing value
- calculate the original value and the new value by setting up an equation to represent the situation and solving for the missing value
- calculating sales tax and discounts

Students engage in Mathematical Practice 1: Make sense of problems and persevere in solving real life, multi-step mathematical problems involving percent by writing and solving equations to represent problems involving simple interest.

**Key vocabulary: **

- discount
- monthly payments
- percent change
- percent decrease
- percent increase
- sales tax

**Special materials needed:**

- calculators (as needed)
- graph paper