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.
- Classify triangles based on angle measurements and side lengths.
- Let’s sort triangles.
Materials to Copy
- Card Sort Triangles (Grade 5)
- Create a set of cards from the blackline master for each group of 2.
- Gather materials from previous activity:
- Triangle Cards
|Activity 1||20 min|
|Activity 2||15 min|
|Lesson Synthesis||10 min|
Teacher Reflection Questions
- 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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