Shapes and Their Perimeter

Lesson 7

Math

Unit 5

3rd Grade

Lesson 7 of 16

Objective


Find perimeter of shapes with all side lengths labeled.

Common Core Standards


Core Standards

  • 3.MD.D.8 — 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.

Foundational Standards

  • 3.OA.D.8

Criteria for Success


  1. Find the perimeter of a shape in which all side lengths are labeled.
  2. Write an equation to represent the perimeter of a shape (optionally including simplified equations, such as a multiplication equation for a regular polygon) (MP.2).
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Anchor Tasks


Problem 1

What do you notice? What do you wonder?

Guiding Questions

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References

Illustrative Mathematics IM Grade 3 Unit 7 Lesson 8 Activity 1 Problem 1

IM Grade 3 Unit 7 Lesson 8 Activity 1 Problem 1, accessed on Nov. 14, 2022, 4:44 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem 2

Find the perimeter of each shape below. Show or explain your work.

a.   

b.   

c.   

Guiding Questions

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Problem Set


Answer Keys

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Discussion of Problem Set

  • What multiplication equation can you write to represent the perimeter of the shape in #1(b)? In #1(f)?
  • Did anyone use any mental strategies to find the perimeter in #2? Which side lengths did you add together first to make the computation easier? Why?
  • Which shape has a greater perimeter in #3? How do you know? Did you calculate the perimeter differently for each shape? Why?
  • Who is correct in #4, Michael, Jackson, both of them, or neither of them? Why? 

Target Task


Problem 1

Heather’s rectangular patio, shown below, is 10 meters long and 18 meters wide. What is the perimeter of her patio? 

Problem 2

Darryl’s patio has a different shape, shown below. 

a.   What is the perimeter of Darryl’s patio?

b.   Darryl says his patio has a larger perimeter than Heather’s patio. Is he correct? Explain how you know.

Student Response

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Student Response

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Additional Practice


The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Extra Practice Problems

Answer Keys

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Word Problems and Fluency Activities

Word Problems and Fluency Activities

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Lesson 6

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Lesson 8

Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Attributes of Two-Dimensional Shapes

Topic B: Understanding Perimeter

Topic C: Distinguishing Between Area and Perimeter

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