Practice Exterior Angle Theorem in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

An exterior angle of a triangle equals the sum of the two non-adjacent (remote) interior angles.

Imagine standing at one corner of a triangular park and looking along one side. The exterior angle is how far you'd turn to look back along the other side. That turn combines the 'bends' at the other two corners—it equals their angles added together.

Example 1

easy
In a triangle, two interior angles are 65° and 48°. An exterior angle is formed at the third vertex. Find the exterior angle.

Example 2

medium
In \triangle ABC, the exterior angle at C is 130°. If \angle A = 5x° and \angle B = 3x + 2°, find the value of x and both interior angles.

Example 3

easy
An exterior angle of a triangle measures 140°. One of the remote interior angles is 75°. Find the other remote interior angle.

Example 4

hard
Prove that an exterior angle of a triangle is always greater than either of the two remote interior angles.
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