Cell Phone Plans

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Objective

Students will be able to model with systems of equation from a more advanced perspective. The equations take on a more realistic context and the focus is on the meaning of the resulting system. Students will be able to use the model of their system to show the benefits and limitations of different cell phone plans.

Big Idea

Students love to send text messages and some have to pay for their own cell phones. This lesson turns the tables and puts the students in the position of pitching cell phone plans to consumers. They use their knowledge of systems of equations to make gra

Lesson Author

James Bialasik

Amherst, NY

Grade Level

Ninth grade

Subjects

Math

Algebra

modeling

Standards

HSA-CED.A

Create equations that describe numbers or relationships.

HSA-CED.A.1

Create equations and inequalities in one variable and use them to solve problems. Include equations arising from linear and quadratic functions, and simple rational and exponential functions.

HSA-CED.A.2

Create equations in two or more variables to represent relationships between quantities; graph equations on coordinate axes with labels and scales.

HSA-REI.C.6

Solve systems of linear equations exactly and approximately (e.g., with graphs), focusing on pairs of linear equations in two variables.

MP1

Make sense of problems and persevere in solving them.

MP2

Reason abstractly and quantitatively.

MP3

Construct viable arguments and critique the reasoning of others.

MP8

Look for and express regularity in repeated reasoning.

Opening

15 minutes

Environment: Students should work in pairs or small groups (no more than 3) to complete this task. Each team is encouraged to come up with the most appealing and understandable representation of the three plans that could be used to help sell each plan to consumers.

We will start out by revisiting the fitness center question. Students can work in their teams to discuss a summary of what this graphical representation shows us. This, once again, requires students to explain the situation based off of a mathematical model(MP4). Students will also be formulating and explaining mathematical ideas within their groups and to the whole class in service of standard MP3.

Investigation

15 minutes

Differentiation: Two versions of this task are provided. Version A (page 1) allows students access to the task without being bogged down by decimal y-intercepts. Version B (page 2) will be used with the majority of students and offers a more realistic representation of cell phone plans.

This question allows students to grapple with a similar type of modeling question around the graphical represenation of cell phone plans. Once students write the variables and define their equations they need to find a way to use their graphical representation to show the benefits of each cell phone plan. This can be done in a variety of ways but the key is for each team to make their data understandable to the average consumer.

Students will also be writing a summary of each plan that will make it sound attractive to a certain type of consumer. Additional information and a table showing the range of each plan has been provided as a scaffold for version A of this task.