Exploring Angle Relationships

Name:

Date:

📐 Part 1: Angle Classification and Estimation

1. Look at each angle and classify it. Circle the correct answer:

Angle A: 45°

Acute

Right

Obtuse

Straight

Angle B: 120°

Acute

Right

Obtuse

Straight

2. Without using a protractor, estimate the size of this angle: ∠ABC = _______°

Now measure with a protractor. Actual measurement: _______°

Difference between estimate and actual: _______°

3. Which strategy did you use to estimate the angle? Tick all that apply:

Compared it to a right angle (90°)

Used my arms to mimic the angle

Looked for half or quarter turns

Other: ___________________

🔄 Part 2: Angle Relationships

4. Two intersecting lines create four angles. If one angle measures 65°, what do the other three angles measure?

Angle opposite to 65°: _______° The other two angles: _______° each

5. Complete these angle relationships:

a) Two angles are complementary if they add up to _______°

b) Two angles are supplementary if they add up to _______°

c) If one complementary angle is 35°, the other angle is _______°

d) If one supplementary angle is 110°, the other angle is _______°

6. Look at angles on a straight line. If three angles on a straight line measure 45°, 65°, and x°, find the value of x.

x = _______°

🧩 Part 3: Problem Solving

7. In the drawing space below, sketch two intersecting lines and label all four angles. Mark one angle as 40° and calculate the other three angles.

8. Real-world angles: A door opens from 0° (closed) to 90° (fully open). If the door is opened to 35°, how many more degrees does it need to open to be fully open?

9. Explain in your own words: Why do angles on a straight line always add up to 180°? Use an example in your explanation.

10. Challenge: If you fold a piece of paper to create an angle, then fold it again to make the angle smaller, what type of angle relationship are you creating? Explain your reasoning.