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
Materials to Gather
Required Preparation
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
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)