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JAMB Mathematics 1988 Question 36

Question 36

Angles and Polygons

Four interior angles of a pentagon are 90° − x°, 90° + x°, 110° − 2x°, 110° + 2x°, Find the fifth interior angle.

  1. A.110°
  2. B.120°
  3. C.130°
  4. D.140°.
Show the answer and explanation

Answer: D (140°.)

Explanation

A pentagon's angles add up to 540°. The four given angles add up to 400° (the x terms cancel), so the fifth is 140°.