Lesson 8
Sort Triangles
Lesson Purpose
Lesson Narrative
The purpose of this lesson is to sort triangles into categories, recognizing right triangles as a category. Students also examine side lengths and notice that sometimes all 3 side lengths are different, sometimes 2 side lengths are equal, and sometimes all 3 side lengths are equal. Students identify right triangles and examine the possible angles that a triangle can have. For example, there are triangles with 3 acute angles but a triangle can only have one right or obtuse angle. Students should have access to straight edges, protractors, and patty paper throughout this lesson.
 Engagement
 MLR7
Learning Goals
Teacher Facing
 Classify triangles based on angle measurements and side lengths.
Student Facing
 Let’s sort triangles.
Required Materials
Materials to Copy
 Card Sort Triangles (Grade 5)
Required Preparation
Activity 1:
 Create a set of cards from the blackline master for each group of 2.
Activity 2:
 Gather materials from previous activity:
 Triangle Cards
Lesson Timeline
Warmup  10 min 
Activity 1  20 min 
Activity 2  15 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Suggested Centers
 Which One? (K–5), Stage 7: Grade 5 Shapes (Addressing)
 How Are They the Same? (1–5), Stage 5: Grade 5 Shapes (Addressing)
 How Are They the Same? (1–5), Stage 4: Grade 4 Shapes (Supporting)
Print Formatted Materials
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Additional Resources
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