Test your understanding of exterior angles at a vertex.

Try to answer the questions before checking the answers at the bottom of the page.

Question 1

If one exterior angle is 80°, what is the other exterior angle?

A) 40°
B) 80°
C) 160°

Question 2

If one exterior angle is 120°, what is the other exterior angle?

A) 60°
B) 90°
C) 120°

Question 3

One exterior angle is x
The other is x + 20

Find x.

A) 10°
B) 20°
C) 30°

Question 4

One exterior angle is 2x
The other is x + 30

Find x.

A) 20°
B) 30°
C) 40°

Question 5

Why are the two exterior angles equal?

A) Because they are adjacent angles
B) Because they are vertical angles
C) Because they are interior angles

Answers

1️⃣ B – 80°

2️⃣ C – 120°

3️⃣ B – 20°

4️⃣ B – 30°

5️⃣ B – Because they are vertical angles

Practice

• More Examples

• Take the Quiz

Continue Learning

1. Types of Triangles
2. Triangles (Basics)
3. Sum of Angles of a Triangle is 180° (Proof)
4. Find the Missing Angle of a Triangle
5. Sum of Exterior Angles of a Triangle (Proof)
6. Exterior Angle Theorem of a Triangle
7. Two Exterior Angles at a Vertex are Equal (Proof)
8. Two Exterior Angles are Equal at a Vertex (Quick Proof)

Navigation

• Back to Triangles
• Back to Home