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JAMB Mathematics 2015 Question 6

Question 6

Angles and Polygons

In the diagram below PQ is parallel to RS calculate the value of x

Diagram for this question
  1. A.20°
  2. B.40°
  3. C.60°
  4. D.80°
Show the answer and explanation

Answer: B (40°)

Explanation

The angle at the crossing next to 100° is 180° − 100° = 80° (angles on a straight line). In the top triangle, ∠Q = 180° − 60° − 80° = 40°. x is alternate to ∠Q because PQ∥RS, so x = 40°.