Shapes and Their Perimeter

Lesson 6

Math

Unit 5

3rd Grade

Lesson 6 of 16

Objective


Find perimeter of polygons whose sides are marked with unit length marks by counting the unit lengths.

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.

Criteria for Success


  1. Find the perimeter of a polygon marked with unit length marks by counting the unit lengths. 
  2. Draw shapes with different perimeters on dot paper. 
  3. Understand that different shapes can have the same perimeter.

Tips for Teachers


Lesson Materials

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Anchor Tasks


Problem 1

Find the perimeter of each shape. Show or explain your reasoning.

a.   

b.   

c.   

d.   

Guiding Questions

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References

Illustrative Mathematics Grade 3 Unit 7 Lesson 6 Activity 2

Grade 3 Unit 7 Lesson 6 Activity 2, accessed on Nov. 14, 2022, 3:44 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

a.   On Dot Paper Template, draw two shapes with each perimeter.

  1. 12 units
  2. 26 units
  3. 48 units

b.   Now try it on your own:

  1. With a partner, choose a length. Then, draw your own shape with that perimeter on Dot Paper Template.
  2. Share the shapes you drew and discuss how they are alike and how they are different.  

Guiding Questions

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References

Illustrative Mathematics Grade 3 Unit 7 Lesson 7 Activity 2

Grade 3 Unit 7 Lesson 7 Activity 2, accessed on Nov. 14, 2022, 4:26 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 Set


Answer Keys

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Discussion of Problem Set

  • How did you find the perimeter of the shapes in #2? Is there more than one way to find the perimeter of certain shapes?
  • How is it possible for different shapes to have the same perimeter? 

Target Task


Problem 1

Find the perimeter of the shape below. Show or explain your reasoning.

Problem 2

Draw a shape below with a perimeter of 20 units.

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 5

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Lesson 7

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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