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JAMB Mathematics 1989 Question 33

Question 33

Angles and Polygons

A regular polygon of (2k + 1) sides has 140° as the size of each interior angle. Find k.

  1. A.4
  2. B.4½
  3. C.8
  4. D.8½.
Show the answer and explanation

Answer: A (4)

Explanation

Each exterior angle is 180° − 140° = 40°, so there are 360 ÷ 40 = 9 sides. Then 2k + 1 = 9 and k = 4.