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WAEC Mathematics 2009 Question 47

Question 47

Triangles and Quadrilaterals

The angles of a triangle are (x + 10)°, (2x − 40)° and (3x − 90)°. Which of the following accurately describes the triangle?

  1. A.It is a scalene triangle
  2. B.It is a right angled isosceles triangle
  3. C.It is an equilateral triangle
  4. D.It is an isosceles triangle but not right angled.
Show the answer and explanation

Answer: C (It is an equilateral triangle)

Explanation

6x − 120 = 180 gives x = 50, so the angles are 60°, 60° and 60°: equilateral.