# Lesson Part 2A

## lesson part 2a

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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.

## lesson part 2a

9th Grade Math - Modeling through Geometry: Circumference of a Cup’s Roll
Molly McNinch, San Lorenzo Unified School District, Woodside High School, Woodside, California

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Previous:  Lesson Part 1C

MOLLY MCNINCH: I'm going to introduce to you guys this new piece of technology that you guys didn't have last class. So it is the “roll radius calculator.” Okay, so, yesterday when you guys were -- oh sorry, last class when you guys were doing this, you kept asking, “Can we use a calculator? Can we use a calculator?” Now there's a cup-rolling calculator that you guys are going to be able to use. So this is going to be linked on School Loop, and so you guys are going to be able to grab a Chromebook and look at this. Now let's get some values. Okay. So somebody shout out a number.

STUDENT: One.

MOLLY MCNINCH: We'll use 10 here. We'll use the slant length of one, and then I need one more number.

STUDENT: Two.

MOLLY MCNINCH: Two. Okay. Narrow diameter is two. Oh gosh, this happened last time ... Okay, two. All right, now, the roll radius -- it's not going to roll the cup. I know, that'd be kind of cool, but it just calculates right here. So you can put in any value, any value. Trust me. Let's put in, well, positive values ... Let's put in 100 for the ... There it is ... 100 for the wide diameter. Let's see what happens there, and let's look at the narrow diameter. So you have this as your last cup, Cup H, where the narrow diameter is zero. So what do you guys think if the slant length is one, the wide diameter is 100 inches, this is a very bad cup. Okay, so the slant height and the radius, the roll radius, would be one inch.

You guys are going to get Chromebooks. They're right behind Mr. Wieser, and you guys, one per table. The link again, it's on School Loop, or you can just copy it from up here. I'll leave this up here. All right. Now you can collect all types of data, and while you guys are working on that, I'm going to hand out a piece of poster paper for you to start putting a thought process on. You guys are creating a “status poster,” so I want to see the status of your problem.

So you're thinking ... You may not get to a solution today, that's fine. I just want to see how you're thinking about it. Now you might get to a solution today, which is great. All right. So the person who has the birthday -- who had the most recent birthday, you are going to grab the Chromebook. All right, go.

You guys have cups. You can roll your cups on the ground. Roll them. That's why you got the cups. Go for it, Cole.

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."