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WAEC Mathematics 2009 Question 20

Question 20

Angles and Polygons

The interior angles of a pentagon are (2x + 5)°, (x + 20)°, x°, (3x − 20)° and (x + 15)°. Find the value of x.

  1. A.80°
  2. B.70°
  3. C.65°
  4. D.40°
Show the answer and explanation

Answer: C (65°)

Explanation

A pentagon's angles add to 540°: 8x + 20 = 540, so x = 65.