Money Math · Lesson Plan

Evaluating Expressions Involving Money

Businesses use algebraic expressions to model revenue: a fixed price times a variable number of items sold. This lesson teaches students the difference between an expression and an equation, how to write a money expression (like $4.55x for sundae sales), and how to evaluate it by substituting a value for the variable. Students write and evaluate ten money expressions.

Grades 6–9 Lesson Plan 30–45 minutes Free Lesson

Evaluating expressions involving money lesson illustration

For Teachers

Lesson at a glance

Topic: Money Math
Grade Level: Grades 6–9
Resource Type: Lesson + Worksheet
Estimated Time: 30–45 minutes
Format: Lesson + worksheet + answer key
Materials: Printable lesson, worksheet, answer key, calculator

What Students Learn

Learning objectives

Distinguish an expression from an equation
Write an algebraic expression for a money situation
Identify the fixed cost and the variable factor in a revenue model
Evaluate an expression by substituting a value for the variable
Apply expressions to real sales and revenue scenarios

Materials

What you’ll need

Printed copies of the lesson and worksheet (one per student)
Calculators
Pencils
Whiteboard or projector for worked examples

Key Terms

Vocabulary

Expression: A statement with numbers, variables, and operations, but no equals sign.
Equation: A statement that two quantities are equal; it has one solution.
Variable: A letter that stands for an unknown or changeable amount.
Evaluate: Find the value of an expression by substituting a value for the variable.
Fixed cost: The set price or cost that does not change.
Revenue: The money a business takes in from sales.

For Teachers

Lesson plan

Estimated time: one 30–45 minute class period.

Lesson sequence

Introduction (5 min). Show 3x − 1: why is this an expression and not an equation?
Teach the model (12 min). Use the ice-cream-shop example ($4.55x): identify the fixed price and the variable, then evaluate for 25 and 8 sundaes sold.
Worksheet (15 min). Students write an expression with a variable and evaluate it for ten sales scenarios.
Review (8 min). Check answers with the answer key and discuss how businesses use expressions for revenue.

Assessment

Assess the completed worksheet against the included answer key.

Discussion

Discussion questions

What is the difference between an expression and an equation?
How do you write an expression for a fixed price times a variable number sold?
What does it mean to evaluate an expression?
Why might a business want a single expression it can evaluate for any number of sales?
Can the same expression give different values? Explain.

Printable Lesson, Worksheet & Answer Key