The teachers in my grade level were instructed to insert a circle unit (just the basics folks) into the scope and sequence for the advanced classes this year. The idea of teaching circles made me happy because I loved teaching circles to my fifth graders; back when I taught at the elementary level. One activity based on the now defunct Growing with Mathematics program involved students’ self-discovery of the pi ratio. Although I used the activity as a brief introduction, I knew I needed to up my game for my seventh graders.
Upon my searching of all circle lessons (wow there are so many!), I stumbled across Andrew Stadel’s 3-Act Math plan for Rolling Tires. Essentially, Mr. Stadel is rolling two different sized tires towards a tower of toilet paper on a makeshift table. That is the premise: toilet paper and tires. Naturally the students were captivated.
I had rehearsed my 3 act math questioning technique with a few Dan Meyer lessons already, so I felt prepared. I showed act one and asked the students to discuss the questions that came to mind. Oh my goodness, they couldn’t get their questions out fast enough. “Will the tire knock down all of the toilet paper? Will the tire hit the target? Is the tower of toilet paper sitting on a table or something else? How quickly are the tires rolling? What is the diameter of each tire? What is the circumference? How many times does each tire need to rotate to get to the target?”
Many students asked me to replay the video over and over again. I was instructed to pause it at certain points, and conversation exploded in the room. The conversations were all about math, geometry, and calculations in real life and it must be said, the students and I were happy.
I asked my student investigators, before showing act two, to consider what specific pieces of information they would want to be provided with in order to satisfy their own varying levels of curiosity. It was the moments following that question which proved Mr. Stadel created a genius lesson. Without saying another word, my math family began to debate each other about the merits of having the radius, diameter, or circumference of each circle. In the middle of the debate, one of the students (I will call her Jan) interjected, “Hey, it doesn’t matter which piece of information we have, if we have the radius, we can find the area, circumference, and diameter. We already know pi is a constant ratio.”
Boom. Just like that, that one student changed the course of the classroom conversation. I asked the other students to clarify Jan’s comments to each other as I walked around and listened in on their dialogue. As I checked in with the students, it became clear that they all understood what she meant and I had this lesson to thank for the reinforcement.
I then showed act 2, which presented the diameter of each tire, the distance of the tire track, and the distance from the tire to the target (if it actually hit the bullseye). The question Mr. Stadel presented, which many students had asked in their own inquiry, was how many rotations would it take for each tire to hit the target and would it actually hit the target?
The students worked furiously and shouted out numbers to each other regarding the circumference. One student started to calculate the area and her partner corrected her with a visual. She actually rolled her water bottle on its side and demonstrated why circumference (kind of like the perimeter) would be important information to answer the question. She asked if I still had string left over from the other lesson and showed her how the length of the string would be helpful to see the distance each rotation covered on the ground.
When most students arrived at their own conclusions (most saw no reason that both tires would not hit the target, but questioned whether or not the force would be powerful enough from the smaller tire to knock all of the toilet paper over), I asked if they were ready to view act three and most responded yes. However, one student protested, “No, don’t show it yet, wait!!! I am not done!” This is a math teacher’s dream.
We all agreed to wait a few more minutes, and then I played act three. The students screamed when the big tire hit the target and complained endlessly when the small tire missed the target. Questions continued to abound.
“Why did he miss? Was his aim bad? Did it have something to do with the tire being smaller? Why did he highlight the central angle of the circle? Why is that significant?”
I don’t need to describe this lesson any further because it is clear that it had students going beyond any math textbook exercise and yet still provided so much actual understanding of a concept. As I continue to search for lessons that produce results like these I must give Mr. Stadel a huge and grateful shout out for this lesson. Mr. Stadel, I am officially a big fan!!!