If the interior angle of a regular polygon is 108°, then it is a -

Concept: For any regular polygon, the interior angle and the exterior angle are supplementary (interior + exterior = 180°), and the sum of all exterior angles of a polygon is always 360°. So the number of sides n = 360° ÷ exterior angle.

Applying this to the given angle:

1. Exterior angle = 180° − interior angle = 180° − 108° = 72°

2. Number of sides = 360° ÷ exterior angle = 360° ÷ 72° = 5

3. A polygon with 5 sides is a pentagon.

Cross-check: for a regular pentagon (n = 5), interior angle = (n − 2) × 180° ÷ n = 3 × 180° ÷ 5 = 108°, which matches the given value, confirming the answer.

∴ The polygon is a Pentagon.