Curriculum  /  Math  /  3rd Grade  /  Unit 5: Shapes and Their Perimeter  /  Lesson 1

Shapes and Their Perimeter

Lesson 1

Math

Unit 5

3rd Grade

Lesson 1 of 16

Objective

Compare and classify polygons.

Common Core Standards

Core Standards

  • 3.G.A.1 — Understand that shapes in different categories (e.g., rhombuses, rectangles, and others) may share attributes (e.g., having four sides), and that the shared attributes can define a larger category (e.g., quadrilaterals). Recognize rhombuses, rectangles, and squares as examples of quadrilaterals, and draw examples of quadrilaterals that do not belong to any of these subcategories.

Foundational Standards

  • 2.G.A.1

Criteria for Success

  1. Classify polygons according to their attributes, like number of sides and angles, and justify this classification (MP.2, MP.3, MP.5).
  2. Understand that a polygon is a closed, flat shape with straight sides.
  3. Understand that a triangle is a polygon with three sides and three angles.
  4. Understand that a quadrilateral is a polygon with four sides and four angles.
  5. Understand that a pentagon is a polygon with five sides and five angles.
  6. Understand that a hexagon is a polygon with six sides and six angles.
  7. Understand that the angle in a shape is the part where two sides meet.
  8. Understand that a right angle is a corner that resembles the corners in a square.
  9. Understand that a regular polygon is a polygon with sides of equal length and angles of equal measure.
  10. Identify sides of equal length, angles of equal measure, and right angles in polygons.

Tips for Teachers

  • Students have learned much of the vocabulary used in today’s lesson in prior grade levels, but not all. New vocabulary includes polygon and regular polygon.
  • As a supplement to the Problem Set, students can play “3 Card Shape Match,” “Shape Sorting,” or “Guess My Shape,” which can be found in the Preferred Tasks of 3.G.1 - About the Math, Learning Targets, and Rigor by the Howard County Public School System.

Lesson Materials

  • Polygons Template (1 per student or small group) — See Anchor Task 1 to see how to prepare this material before the lesson.
  • Ruler (1 per student or small group) — This can be any tool used to verify equal lengths, e.g., the edge of a piece of paper, etc.
  • Right-angle tool (1 per student or small group) — This can be any tool used to verify right angle measures, e.g., a piece of paper folded in half twice or the corner of a piece of paper.
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Anchor Tasks

25-30 minutes

  1. Sort these shapes (cut out from Polygons Template) into groups. You may sort them any way you want and into as many groups as you want. Be prepared to explain how you sorted the shapes. 
  2. Sort them another way.

Guiding Questions

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Student Response

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Problem Set

15-20 minutes

Discussion of Problem Set

  • I chose Polygon W for #3. Do you agree or disagree with my choice? Why?
  • Do you agree or disagree with Jenny in #5? Why? Were there other quadrilaterals that Jenny didn’t identify? What about Polygon O in #3?  
  • What vocabulary term can you use to describe the shape in #6a? What other words can you use to describe it? Would you consider this polygon to be a regular polygon? Why or why not?
  • What has to be true about the figure you drew in #6b? What are some ways in which the figure you drew could vary from the figure others drew while still being correct?
  • What vocabulary term can you use to describe all of the shapes on the Problem Set? Why?

Target Task

5-10 minutes

Use the polygon below to answer the following questions.

a.   How many angles are in this polygon?

c.   What word best describes the type of polygon this is?

d.   Is this polygon a regular polygon? Explain why or why not.

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.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Next

Compare and classify quadrilaterals.

Lesson 2
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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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