standard_description: Solve real world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters.
problem_activity: Narrative
The purpose of this activity is to deepen students’ understanding that a shape can belong to multiple categories because of its attributes. Students analyze shapes and determine all the ways that each one could be named. The names may refer to a broad category such as triangle or quadrilateral, or a narrower subcategory such as rhombus or rectangle. As they name the different categories students need to be precise both about the meaning of the categories and verifying the properties of the different shapes (MP6).
MLR8 Discussion Supports.
Synthesis: For each observation that is shared, invite students to turn to a partner and restate what they heard using precise mathematical language.
Advances: Listening, Speaking
Engagement: Provide Access by Recruiting Interest.
Leverage choice around perceived challenge. Invite students to select at least 4 of the 6 problems.
Supports accessibility for: Organization, Attention, Social-Emotional Skills
Launch
Groups of 2
“Look at the quadrilateral in the first problem. Work independently to circle all the names that you could use to describe the quadrilateral. Be prepared to share your reasoning.”
1 minute: independent work time
“Discuss your responses and reasoning with your partner.”
2 minutes: partner discussion
Share responses.
Activity
“Complete the rest of the problems independently. Be prepared to explain your reasoning.”
3–5 minutes: independent work time
“Now, discuss your answers with your partner. Be sure to explain your reasoning for each way you described the shape. Also, be sure to ask your partner if you have any questions about their reasoning.”
5–7 minutes: partner discussion
Monitor for students who notice that some shapes can be described using multiple terms.
Student Facing
Select
all
the ways you could describe each shape. Be prepared to explain your reasoning.
1
[IMG]
triangle
quadrilateral
square
rhombus
rectangle
2
[IMG]
triangle
quadrilateral
hexagon
rhombus
rectangle
square
3
[IMG]
triangle
quadrilateral
pentagon
rhombus
rectangle
square
4
[IMG]
triangle
quadrilateral
hexagon
rhombus
rectangle
square
5
[IMG]
hexagon
quadrilateral
triangle
square
rectangle
rhombus
6
[IMG]
hexagon
quadrilateral
triangle
rhombus
rectangle
square
Student Response
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Advancing Student Thinking
If students use only one name for a shape that can be named in multiple ways, consider asking:
“How did you describe the shape?”
“Are there any other names that could be used to describe the shape?”
Activity Synthesis
Select 1–2 students to share the terms they selected for each of the last four quadrilaterals and their reasoning.
Consider asking:
“Who can restate _____’s reasoning in a different way?”
“Does anyone want to add on to _____’s reasoning?”
“Do you agree or disagree? Why?”
“The last shape can be described with 4 of the choices. How is it possible that it can be described in so many ways?” (It is a quadrilateral because it has 4 sides. It is a rhombus because it’s a quadrilateral with 4 sides that are the same length. It is a rectangle because it has 4 right angles and 2 pairs of sides that are the same length. It is a square because it has 4 sides that are the same length and 4 right angles. The last three are more specific descriptions of a quadrilateral.)


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