My Contract is Up… Who has the

best deal?

• Graphing Linear Equations Using Graphing Calculator

Lesson Objectives

• How to use linear equations to describe and interpret real-life situations?

• How to use graphing calculator to visualize linear relationships?

Problem

Your cell phone plan has just expired with Company X and you want to switch companies. Below is the information you gathered regarding the plans you are considering:

• SPRINT has an initial monthly charge of $25.75 for providing their services and charges 30 cents for every minute.

• VERIZON charges $55.50 per month and 10 cents for every minute.

• CINGULAR does not have an initial monthly charge. It charges 75 cents for every minute.

Note: No more free minutes included in plans!

Task

You decided to look deeply into these plans before making a decision. You are to create the following:

Equations that represent each of your options

A graphical representation of the information you have gathered

Student Activity

come up with the equations that represent cell phone plans (WORK AS A GROUP, make sure everyone in your group understands what each element in the equation represents)

graph the functions in the calculators replicate the graph on your individual

graph paper. looking at your graph answer the

questions given in worksheet

Think about this

During what interval does SPRINT offer the best deal?During what interval does CINGULAR offer the best deal? During what interval does VERIZON offer the best deal?Which company would you choose if you talked an average of 100 minutes per month?What if you talked an average of 200 minutes per month?When do SPRINT and VERIZON charge the same rate and what is that rate? How do you chose which plan is best for you?

Resources

Writing Linear Equations

Graphing Linear Equations

Solving Systems of Equations Graphically

Standards

MST3.MR1: Students use mathematical reasoning to analyze mathematical situations, make conjectures, gather evidence, and construct an argument.

MST3.MM4: Students use mathematical modeling/multiple representation to provide a means for presenting, interpreting, communicating, and connecting mathematical information and relationships.

MST3.PF7: Students use patterns and functions to develop mathematical power, appreciate the true beauty of mathematics, and construct generalizations that describe patterns simply and efficiently.

MST3.alt.PF4: Students use mathematical patterns in a real-world situation.