4MA1/2F Jan 2019, Question 13: Multi-Step Angle Reasoning
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2F (Foundation) · Calculator · 5 marks
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The question, in short
In the figure, ABD is isosceles with AB = DB, DCE is straight, angle ABD = 48°, angle BCE = 68° and reflex angle ADC = 243°. Find angle y, justifying each step.
Summarised in our own words. Use the official paper for the exact wording and the diagram.
Solution · 5 marks
- 1Angle ADC = 360 − 243 = 117° (angles at a point add to 360°)
- 2Angle BDA = (180 − 48) ÷ 2 = 66° (base angles of an isosceles triangle are equal)
- 3Angle BDC = 117 − 66 = 51°
- 4Angle BCE = angle BDC + y (exterior angle of triangle BCD equals the two opposite interior angles)
- 5y = 68 − 51 = 17
Answer17
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