Skip to main content


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

Clip 5/19: Modeling through Geometry: Lesson Part 1A


At the beginning of her lesson, Molly McNinch asks her students to talk to a peer and describe what it means to “model a problem.” Her students share their ideas: modeling a problem means making a diagram, a graph, a chart, a table. Molly challenges her students to “think about ways that you can organize your data that would be beneficial to getting to the solution.” She displays videos of different rolling cups that her students had watched previously, with the purpose of understanding how the diameter of the cup and the roll radius relate to each other, and how different objects behave differently.

Teacher Commentary

I try to honor that they're children still. Because I work primarily with freshmen, really. I have 13 sophomores out of all of my students. I try to keep in mind they're still young, but ... When I start to get down on myself about teaching, I try to remind myself I do this because I do care. If you ask my students to describe my classroom, they’ll say, "Yeah, it's pretty chill." Because it's mellow and they're small classes and they move at a pretty comfortable pace. My Geometry classes, we have a lot of fun.... So if a new student came into my Geometry class they would probably hear a lot of, "It's pretty mellow in here, but the work's really hard." Which is exactly what I want. I want it to be a safe environment for them, but you have to work.