Clip 4/11: Area and Perimeter Lesson Part 1C

Overview

Robin’s 3rd-grade students sit in groups around the classroom, working with large graph paper. Robin makes explicit that the tiles the students have available for their work are congruent with the scale of the graph paper. She gives students the area of 12 and asks them to create a rectangle that has the area of 12. Students select 12 tiles from their bag and get to work, talking with each other about their process and making sure their tiles align with the grid of the graph paper. Robin then asks what math problem they could write down to go with the array they built, and why. Students discuss with each other. (“We can’t do 8 times 6 because it won’t go with 12, which is our area.”) Robin then asks students to draw the shape they formed from tiles on the paper, along with the math problem they had to find their area. She then asks groups to figure out the perimeter. As they work, some students make use of anchor charts, and others ask what unit they would use for perimeter (“inches” or “square inches”?). Robin engages groups in questioning and encourages them to keep going. (“What kind of a math problem could you write to show me the perimeter? You tell me!”)

Teacher Commentary

I did notice some of my students used our poster that talks about area and perimeter, which I found was interesting because I actually haven't discussed that poster with them, the anchor chart with them. I found it quite neat that they were referring to it and drawing that information on their own. I know one group was sitting there talking about “No, with perimeter, we need to add,” because that's what the chart had said, but I had not brought any attention to that prior to the lesson. I was excited to see that. I was really intrigued to see how they really dived in. They went ahead with it. I had it there just to see if they will even see it, or even use it. I call them the cheat charts, because they can “cheat.” It's legal cheating.

As they continued their group work, it was very interesting to see them just flipping shapes and saying, “Well, this is a different shape.” I told them “Well, okay, I could see that, but how else can you do it?” And once they got the gist of that, they were able to explore perimeter all on their own. It was all student-led. I did very little — I redirected them, but they were able to figure it out.