Writing and Using a Function Model

Question:
A cell phone plan charges a 15-dollar monthly fee plus 8 cents per minute of talk time. Write a function C of m that gives the total monthly cost in dollars for m minutes of talk time. Then find C of 200 and C of 500, and interpret what these values mean in context.

Writing and Using a Function Model

This lesson introduces linear functions by modeling a real-world cost scenario with a fixed fee and a per-unit rate. Students write a linear function in slope-intercept form, evaluate it at specific inputs, graph it, and interpret the results in context.

In this lesson, you will learn to:
• Write a linear function to model a situation with a fixed fee and a variable rate
• Identify the slope and y-intercept of a linear function and explain their real-world meaning
• Evaluate a linear function at given input values
• Interpret function output values in the context of the original