Blog Post

Rotten Tomatoes, Linear Equations, Ratio and Proportion

This problem came about because I was talking about solving the equation 4x + y = – 14 for y and there was a little confusion about how I could  subtract 4x from – 14.  Although this was really a problem with combining like terms, I figured that now was as good of a time as ever to reinforce the idea of combining like terms.

“Yaletta bought an unknown number of tomatoes at $4 each, but when she got home, she found out that all of the tomatoes were rotten.  In addition, she checked her receipt and realized that the store had charged $14 to carry the tomatoes to the car.  Write an equation to model Yaletta’s total losses.” (as a signed number)

The students seemed to come to the consensus that an appropriate answer would be y = – 4x – 14.

Then I asked these questions as well:
  • What does y represent?
  • What does x represent?
  • What does -4 mean?
  • What does -14 mean?
  • How much would Yaletta lose if she bought 25 tomatoes?  (as a signed number)

What’s even more interesting about this problem for me is that later in the day I was talking about ratio and proportion and so I used this same problem to ask questions such as:

  • Do you think that it’s fair that the $14 dollar charge is fair?  Why or why not?
  • Would it be more appropriate to have a charge proportional to the number of bags of tomatoes carried to the car?
  • What additional information would we need to know in order to make this change to the charge?

By Jon Oaks

College Math Instructor. Tech Enthusiast. Visionary. Creative Genius. But above all, I enjoy what I do. That is why I am a teacher. Because I like to teach.

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