Explain — 2 marks
A gardener is designing a flower bed in the shape of a quadrilateral. The diagram shows the flower bed ABCD with angle ABC marked as 110° and side AB parallel to side CD.
- (a) Explain why angle BCD must be 70°. [1 mark]
- (b) Given that angle BAD is 75°, explain why angle ADC must be 105°. [1 mark]
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- (a) Co-interior/allied angles add up to 180° (or angles on a straight line/add to 180° if using alternate approach)
- (a) 180° − 110° = 70°
- (b) Angles in a quadrilateral add up to 360°
- (b) 360° − 110° − 70° − 75° = 105° (or equivalent method showing correct working)