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JAMB Mathematics 1981 Question 17

Question 17

Triangles and Quadrilaterals

In the figure above, find x in terms of a, b and c.

Diagram for this question
  1. A.a + b + c
  2. B.180° − (a + b + c)
  3. C.a − b + c
  4. D.a + b
  5. E.a + c.
Show the answer and explanation

Answer: A (a + b + c)

Explanation

Join the top vertex through the inner vertex. Each exterior angle of a triangle equals the sum of the two opposite interior angles, so the two parts of x add up to a + b + c.