Lesson 10

Ways to Find Angle Measurements (optional)

Lesson Purpose

The purpose of this optional lesson is for students to use the attributes of figures (symmetry, equal side lengths, right angles) to reason about angle measurements.

Lesson Narrative

Previously, students analyzed the attributes of two-dimensional figures and used them to find side lengths and perimeters. In this lesson, students use the attributes of figures to find unknown angle measurements and to practice drawing line-symmetric shapes. Both activities in the lesson deepen students’ understanding of line symmetry. They also allow students to apply knowledge of angles from an earlier unit and integrate it with newer ideas from this unit. Because the work here is not required by the standards, however, this lesson is optional.

  • Representation
  • MLR8

Learning Goals

Teacher Facing

  • Find unknown angle measurements using the attributes of two-dimensional figures.

Student Facing

  • Let’s find angle measurements in figures with line symmetry.

Required Materials

Required Preparation

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 25 min
Activity 2 15 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

Today’s lesson presented many opportunities for divergent reasoning strategies. Think about which students haven’t shared their strategies in class lately. Were there missed opportunities to highlight their thinking during recent lessons? How can you take advantage of those opportunities when they arise?

Suggested Centers

  • Which One? (K–5), Stage 5: Grade 4 Shapes (Addressing)
  • How Are They the Same? (1–5), Stage 4: Grade 4 Shapes (Addressing)
  • Compare (1–5), Stage 5: Fractions (Supporting)
  • Compare (1–5), Stage 7: Multi-digit Operations (Supporting)

Print Formatted Materials

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Additional Resources

Google Slides

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PowerPoint Slides

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