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

Clip 8/19: Modeling through Geometry: Lesson Part 2A


Molly McNinch introduces her students to a new tool that they had not used previously: a roll radius calculator. Students use laptops and access the Mathematics Assessment Project’s [roll radius calculator]( Molly demonstrates how to use the calculator, connecting her students’ testing of different quantities with the status poster justification her student groups will create.

Teacher Commentary

When we use a new tool or strategy, I think a lot of my students will notice that it's so incredibly normal to have issues or be confused or pause and stop and redo something or restart. Even our textbook, _Discovering Geometry_, comes along with its own little quirks. So there's some problems in there that I'm like, "Oh my gosh, what are they trying to tell us?" And so the students will say, "Can we do this problem on the board?" And I say, "Sure, let's do it." There have been times where I kind of stop and I turn around and say, "Guys, I'm not sure how to start this." This not only takes shame away from wrong answers, but it allows students to come together to solve a problem collaboratively. Another growth opportunity.

It's great because usually one of the students does [step up to help with the problem]. It's good, because it I think in that sense it shows them, "Oh, yeah. The teacher doesn't know what to do and that happens and it's totally okay." You know? Because a lot of the times the students will have good ideas, or there have been times where one student will have one idea and one student will say, "I got the same answer, but I did it completely differently." Or one time we'll start one way and realize, "Oh, that didn't work, so let's try a different way."