Advanced Mathematics Primary 5 Geometry

In trapezium ABCD, AB is parallel to CD. Given that ∠ADC = 68° and ∠BCD = 75°, find ∠DAB and ∠ABC.

A 112° and 105°
B 68° and 75°
C 68° and 105°
D 112° and 75°
Show Worked Solution

Worked Solution

Step 1: AB ∥ CD with transversal AD. ∠DAB and ∠ADC are co-interior angles. ∠DAB = 180° − 68° = 112° Step 2: AB ∥ CD with transversal BC. ∠ABC and ∠BCD are co-interior angles. ∠ABC = 180° − 75° = 105° Step 3: Verify — angle sum of quadrilateral ABCD: 112° + 105° + 75° + 68° = 360° ✓ Answer: ∠DAB = 112° and ∠ABC = 105°

Correct answer: 112° and 105°

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