Practice: Models and Applications

Question

The Ferris cell phone company has a basic cell phone plan. This plan includes unlimited talk and text but charges a monthly phone charge fee of $21.00 per month plus $6.50 per 1 GB of data that is used for that month.

Write a linear equation that models the monthly cost (C) of the cell phone based on the number of data GB, (d), used.

If your monthly cell phone bill was $45.00, how many GB of data did you use?

Answer 1

There's a fixed and a variable part to this problem and equation.

The fixed part is the $21.00/mo.; the variable part is the number of GB's used in the month.

If C is monthly cost and d is number of GB's then C = 21 + 6.50d

Substitute $45 for C and solve for d for the 2nd part of the question.