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WAEC Mathematics 2015 Question 33

Question 33

Angles and Polygons

In the diagram, QT and PR are straight lines, ∠ROS = (3n − 20)°, ∠POT = 2m, ∠SOT = n, ∠POL = m and ∠QOL is a right angle. Find the value of n.

Diagram for this question
  1. A.35°
  2. B.40°
  3. C.55°
  4. D.60°
Show the answer and explanation

Answer: A (35°)

Explanation

On line QT: 90° + m + 2m = 180°, so m = 30°. On line PR: 2m + n + (3n − 20) = 180°, so 4n = 140° and n = 35°.