Lesson Plan

Classifying Triangles

This Classifying Triangles lesson plan also includes:

Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy Triangle, children go on to create triangles using geoboards and flexible straws, complete a series of worksheets, and, finally, demonstrate their learning on a short quiz.

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CCSS: Adaptable
Additional Tags
Instructional Ideas
  • Use this lesson series to introduce an upper elementary geometry unit on triangles
  • At the end of the series, break students into six groups and have each create a poster describing a different type of triangle; use their work to create a classroom bulletin board
Classroom Considerations
  • A copy of the book The Greedy Triangle by Marilyn Burns is used to introduce the first lesson. If you do not own a copy, one can most likely be found in your school or local library
  • Depending on the availability of materials in your classroom, you may want to consider letting students work on some of the activities with a partner or small group
  • Offers a wide selection of worksheets and activities that support students with learning how to classify triangles
  • A list of necessary materials are included for each of the three lessons
  • Each lesson includes a clear set of procedures, an imbedded assessment, and ideas for reteaching or extending learning about triangles
  • None
Common Core