Triangles — O/L Mathematics

How do I practise Triangles?

1 question with a worked solution

1. In triangle ABC, the side BC is produced to D. If angle ABC = 55° and angle BAC = 65°, find the magnitude of the exterior angle ACD.
   1. A) 60°
   2. B) 110°
   3. C) 120°
   4. D) 130°
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   Correct answer: C) 120°

   By the exterior angle theorem of a triangle, the exterior angle formed by producing a side equals the sum of the two interior opposite angles: angle ACD = angle ABC + angle BAC = 55° + 65° = 120°.

   Show worked solution

   Step 1: State exterior angle theorem: Exterior angle = sum of interior opposite angles. Step 2: Identify angles: Interior opposites are 55° and 65°. Step 3: Calculate sum: 55° + 65° = 120°. Answer: 120°.
   Modelled on: the O/L Mathematics examination pattern

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Where does Triangles fit in the syllabus?

Grade 10 · Term 1