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9th Grade Math - Modeling through Geometry: Circumference of a Cup’s Roll

Clip 11/19: Modeling through Geometry: Lesson Part 3A


Molly McNinch distributes example approaches by three fictional students — “Judi,” “Gerry,” and “Heather” — so that her (actual) student groups can evaluate and critique the approaches of other mathematicians’ work. Molly has color-coded the example work and asks students to look at it in a particular sequence. She asks her students to “think of them as your new groupmates who have new ideas to share, okay? You guys don't know if they're right; they don't know if they're right. So you're just taking their information and using it to help your idea go further.”

Teacher Commentary

With the additional “student work” pieces, it was helpful, I think, for my students to have three separate colors. When I did it in an earlier period, I didn't tell them anything about whether they had solutions, but with this class, I emphasized that neither of these, or none of these, have the solution. It was also helpful to talk about, "Okay. You have three new group members, so we have a red, a yellow, and a blue group member. What does each group member bring to your solution or your ideas that you didn't have before?" Asking "What does each individual new group member bring that you didn't have prior?" is helpful to the students.

A note about making the sheets different colors: whenever there is an opportunity for students to clearly identify something quickly, I go for different colors. It’s easier to say, “Look at the pink paper.” than say “Look at the paper titled ‘Helen’s work.’”