Which statement about the exterior angle of a triangle is correct?

Class 7The Triangle and its PropertiesTriangles

AIt equals the sum of the two opposite interior angles.
BIt equals the adjacent interior angle.
CIt equals the sum of all three interior angles.
DIt is always 90°.

Step-by-Step Solution

By the exterior angle property, an exterior angle equals the sum of its two non-adjacent (opposite) interior angles.

Answer: A) It equals the sum of the two opposite interior angles.

Key idea: Exterior angle property

Extend one side of a triangle past a vertex. The angle formed outside the triangle is the **exterior angle** at that vertex.

**Exterior angle = sum of the two opposite interior angles.**

So if the two non-adjacent interior angles are 50° and 60°, the exterior angle = 50° + 60° = 110°.

Why? The exterior angle and the adjacent interior angle form a linear pair (sum 180°), and the three interior angles also sum to 180°. Subtract: exterior = sum of the other two interior angles.

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