Measuring Angles with a Protractor

🎯 What Will We Learn Today?

A protractor is a special tool for measuring angles. Today we'll learn how to use a protractor to measure any angle accurately!

📚 What Is a Protractor?

A protractor is a semicircular (half-circle) tool marked with degrees from 0 to 180. It's usually made of clear plastic so you can see through it.

The curved edge has two sets of numbers — one going from 0 to 180 clockwise, the other counterclockwise. This lets you measure angles from either direction!

📐 How to Measure an Angle

Step 1: Place the center point of the protractor exactly on the vertex of the angle.

Step 2: Line up the baseline (the 0° line) of the protractor with one arm of the angle.

Step 3: Read where the other arm crosses the numbered scale. That's your angle measurement!

🎮 Let's Measure!

Example: Measure a right angle.

Place protractor center on the vertex

Align baseline with one arm

The other arm points to 90° — it's a right angle! ✓

Try this: Draw an angle and measure it. Then ask a friend to measure it too. Did you get the same answer?

💡 Common Mistakes to Avoid

Using the wrong scale — always start from 0° on the arm you're aligned with

Not placing the center exactly on the vertex

Reading the number too quickly — take your time!

📝 Practice Problems

Draw a 45° angle using a protractor. What type of angle is it?

Measure the corner of a piece of paper. What angle do you get?

Draw angles of 30°, 60°, 90°, and 120°. Label each one.

If you measure an angle and get 95°, what type is it?

🎮 Play a Game!

Practice with Island Chase — compete and sharpen your math skills!