Every kid loves pizza, right?  Well, my students do, and they LOVED their first Mathalicious lesson, Domino Effect.  The best part is that it is one of the sample lessons from Mathalicious so you can try it for free!

This lesson is intended for students in Algebra 1. However I did this lesson with 6th grade students who had not learned linear equations yet. After introducing the lesson, I gave them the student handouts. The student handout was self-explanatory and easy for my 6th grade students to follow.  I gave each student their own set of handouts but let them work in pairs so they had someone to talk through their work with.

I appreciated that there were several related questions.  This made students aware that they had made a mistake in a previous question so they knew they had to go back and rethink it.

The questions were leading enough so that my students (who had not written linear equations yet) were able to summarize their findings.  I was pleasantly surprised that several students even came up with an equation.

Many students ran into trouble in Act 2 on question number 2, when they assumed that the medium topping price was the price of toppings for all pizza sizes.  The layout of the chart alerted most of these students that they had made a mistake when they noticed that a 2-topping small pizza was $10.48, but a 3-topping small was only $10.99.  Other students discovered this when graphing the points.  I noticed that some students did not notice this discrepancy at all, but and let them continue to fill out the chart incorrectly.  To help students discover their mistake, I asked them if they could figure out how much a small, medium, and large 10-topping pizza would be.

Some students went straight to their calculators.  Other students wanted to use their graphs but were not sure that they were allowed to extend the lines.  This was another opportunity for discussing lines and patterns.  They loved this “shortcut” and that it quickly helped them price their 10 topping pizzas.  

After all of the groups had come up with their 10-topping pizza prices, I drew a large chart on the board and had the groups fill in their prices to illuminate the differences.  

Once they saw that other students pizza pricings were different, they had a heated class discussion about who was right.  “Proving” their calculations to each other helped all of the groups realize that the topping price was supposed to be different for differently sized pizzas.  After everyone had time to find and fix their mistakes, they updated the board chart to make sure everyone was now on the same page.

I liked having them find the price of a 10-topping pizza because it prepared them for the big reveal.  My students pretty much lost it when they saw Domino’s actual pricing, since it was so much less than they had calculated.  They all wanted to fix their graphs, which of course, I was thrilled about, so I let them.  Notice the key at the bottom on the picture.  (That is supposed to be thought).

I loved this lesson because it was fun, self-explanatory, and easy to implement.  It was written so that I was able to walk around the room and support students that needed extra assistance or were going down the wrong path.  I did not “teach a lesson”, but at the end of Act 1 several of my students had figured out the equation by going through the questions.

This can be done with younger students, even if you haven’t taught linear equations yet.  In fact, this is a great introduction to the topic of linear equations.  Next time I do this lesson with 6th grade students, I will do this over two days.  The first day I will do Act 1, and then finish with the chart on Act 2.  Then, on the second day I will explore Act 2, questions 3 and 4 in more depth.  Only a few students were able to come up with the equation in Act 1, so I will need more in class time to help them discover this in Act 2.  I anticipate that I can teach students about writing equations of lines and even explore what the y-intercept really means with this lesson.

Pictures of my students finished projects:

PIzza Project Rubric