In this page we practice using the rule:

Sum of exterior angles = 360°

Example 1

Exterior angles are:

100°, 120°, and x

100 + 120 + x = 360

220 + x = 360

x = 140°

Example 2

Exterior angles are:

90°, 150°, and x

90 + 150 + x = 360

240 + x = 360

x = 120°

Example 3

Exterior angles are:

x, x, and 120°

x + x + 120 = 360

2x + 120 = 360

2x = 240

x = 120°

Example 4

Exterior angles are:

x, 2x, and x

x + 2x + x = 360

4x = 360

x = 90°

Example 5

Exterior angles are:

x, 3x, and 2x

x + 3x + 2x = 360

6x = 360

x = 60°

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)

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