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UI Post-UTME Mathematics 2019 (Model questions) Question 18

Question 18

Triangles and Quadrilaterals

In the figure above, the value of x is

Diagram for this question
  1. A.140°
  2. B.100°
  3. C.120°
  4. D.110°
Show the answer and explanation

Answer: A (140°)

Explanation

Join the outer corners to make a big triangle: the small base angles a and b satisfy 80 + 20 + 40 + a + b = 180, so a + b = 40. In the lower triangle x + a + b = 180, so x = 140°.