Lesson 8

Clasifiquemos triángulos

Lesson Purpose

The purpose of this lesson is for students to classify triangles using angle measures and side lengths.

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

  • Clasifiquemos triángulos.

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

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 20 min
Activity 2 15 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

How are students applying what they learned about the hierarchy of quadrilaterals to help them make sense of classifying triangles?

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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Student Task Statements pdf docx
Lesson Cover Page pdf docx
Cool Down Log In
Teacher Guide Log In
Teacher Presentation Materials pdf docx
Blackline Masters zip