Do you really get a free cell phone with your cell phone plan?

prepaid_cell_phoneIn my experience, I have found that teens love (1) their phone and (2) a heated debate. When my grade 8 students were studying linear relationships, I combined those two interests into a activity in which students critically evaluated advertisements for service plans offering free (or discounted) cell phones.

Following the guidance in this task sheet, students compared two cell phone plans: one bring-your-own-phone plan and one free (or discounted) phone plan. They determined the linear relationship for the cost of each plan over time and plotted both equations on a single grid using Desmos.

With  an algebraic equation and a graphic representation of each plan, students considered,

  • In what situation(s) the free (or discounted) phone plan a better deal.
  • In what situation(s) the bring-your-own phone plan a better deal.
  • Which option would be the best for them personally.
  • Which other factors might change their choice.

This was a great introduction to systems of equations, as the concrete, authentic context helped students to consider the significance of the point where the two equations intersect. Moreover, solving the system graphically was a more intuitive entry-point to systems of equations than an algebraic solution. In addition to those benefits, my favourite part of this task is that it allowed student to apply their math skills to be critical consumers, and will hopefully save them (or their parents) a bit of money in the future.

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