Lesson Plan: Types of Triangles: Sides Mathematics • 3rd Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to identify equilateral, isosceles, and scalene triangles by considering the length of their sides.


Students will be able to

  • visually classify triangles as equilateral, isosceles, or scalene,
  • classify triangles by measuring their side lengths in whole units,
  • understand the notation for equal (congruent) sides and use this to classify triangles.


Students should already be familiar with

  • acute, obtuse, and right angles,
  • the notation used for congruent sides in regular polygons.


Students will not cover

  • classifying triangles by their angles,
  • drawing or measuring the sides of triangles.

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