2025 · Q73
The interior angle of a regular polygon exceeds its exterior angle by 120°. How many sides does it have?
Elementary MathematicsQuadrilaterals and Polygons
- A6
- B8
- C10
- D12
Explanation
Interior + exterior = 180 degrees and interior - exterior = 120 degrees, so the exterior angle is 30 degrees. Then n = 360/30 = 12 sides. Solving the linear system directly beats guessing at polygons.