Linear equations

In this lesson for grade seven, students calculate monthly bills for cell phone plans using linear equations.

A lesson plan for grade 7 Mathematics

By Peggy Dickey and Barbara Turner · Adapted by Sharon Abell

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CareerStart lessons: Grade seven

This collection of lessons aligns the seventh grade curriculum in math, science, English language arts, and social studies with potential career opportunities.

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• Learn more about linear equations and mathematics.

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Learning outcomes

Students will use hypothetical scenarios to explore the concept of linear equations.

Teacher preparation

Time required for lesson

Approximately 55-70 minutes. Some homework time may be needed.

Materials needed

• Student handouts:
  • Cell phone charts
  • Linear equation scenarios worksheet
• Linear equation scenarios worksheet answer key
• Overhead projector and pens
• Transparency copies of:
  • Cell phone charts
  • Mock cell phone plans
  • Linear equation scenarios worksheet

Activities

1. Hand out the cell phone charts and project the transparency of the charts on the overhead projector. Ask the students how many of them have cell phones. Ask those who have cell phones what their rate plans are. Fill in the first chart on the overhead according to the students’ rate plans. If the students don’t know their plans, you may project the mock cell phone plans and use them to fill in the chart. Have the students fill in their charts as you work. Make the point that most cell phone plans consist of a set cost per month for a given number of minutes, plus a charge for additional minutes. (5 minutes).
2. Choose one of the plans as an example and use it to fill in the second chart on the overhead. Have students calculate how much the monthly bill would be if the cell-phone user went over his or her monthly plan by 5, 10, 15, 20, 25, 30, 35, and 40 minutes. As you fill in the chart, be sure to write out on the board how you calculate the monthly bill. (10 min.)
3. Ask students if they see a pattern forming; if so, what is it? (Students should answer that they multiply the number of minutes over and the cost per minute and then add the monthly charge.) (5 minutes)
4. Ask the students what the constant amounts are in the calculation. (Answer: The cost per month and cost for additional minutes). Ask them which amount changes in each of the examples. (Answer: The number of minutes over) (5 minutes)
5. Ask the students if they can figure out a mathematical formula that they could use to get the answer each time (use words first and then substitute with x and y). (5 minutes)
6. Independent practice: Hand out the linear equation scenarios worksheet and have the students complete it. (The worksheet lists hypothetical scenarios and asks the students to write out, in words, a formula for each scenario. The worksheet also has them decide for each scenario what the constant amounts and variable amounts are. Students who don’t finish the worksheet in class should finish it for homework. (20 minutes)
7. To wrap up the lesson, ask the students what jobs use these types of skills. (Answers include careers in advertising and marketing, construction managers, accountants and auditors, computer programmers, mathematicians, architects, aerospace engineers, and biomedical engineers. Have students discuss how people in these careers might use linear equations. (5-10 minutes)