# Lesson 9

Use a Protractor to Measure Angles

### Lesson Purpose

The purpose of this lesson is for students to understand $$1^\circ$$ as a measurement of a turn through $$\frac{1}{360}$$ of a circle and to use a protractor to measure angles.

### Lesson Narrative

Before this lesson, students have compared and measured angles using informal tools (analog clocks) and reference angles, all of which were multiples of $$5^\circ$$ or multiples of $$10^\circ$$. In this lesson, students transition to measuring angles in units of $$1^\circ$$.

Students then make sense of one-degree angles in terms of a fraction of a $$360^\circ$$ turn and are introduced to the protractor as a tool of measurement. They make sense of the numbers on the tool and how $$1^\circ$$ angles are shown. They learn to read the measurement of angles whose vertices have been pre-aligned to the center point of a protractor.

Students will continue to add new vocabulary to their personal word walls. In the next lesson, students will further develop their ability to use a protractor by measuring a variety of angles with less support.

• Action and Expression
• MLR2

### Learning Goals

Teacher Facing

• Recognize that 1 degree is a measurement of a $\frac{1}{360}$ turn through a full circle.
• Use tools to measure angles.

### Student Facing

• Let’s use some tools to measure angles.

### Required Materials

Materials to Gather

### Lesson Timeline

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

### Teacher Reflection Questions

The first two activities offered opportunities for students to take multiple solution paths. Were all unique perspectives or strategies heard? Which students were able to share their ideas? Which didn’t get a chance? How can their voices be added into the conversation tomorrow?

### Suggested Centers

• Target Measurements (2–5), Stage 4: Degrees (Addressing)
• Compare (1–5), Stage 5: Fractions (Supporting)