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WAEC Mathematics 2021 Question 16

Question 16

Angles and Polygons

The sum of the interior angles of a regular polygon with k sides is (3k − 10) right angles. Find the size of the exterior angle.

  1. A.60°
  2. B.40°
  3. C.90°
  4. D.120°
Show the answer and explanation

Answer: A (60°)

Explanation

(k − 2) × 180° = (3k − 10) × 90°, so 2k − 4 = 3k − 10 and k = 6. Each exterior angle is 360° ÷ 6 = 60°.