Standard Mathematics Primary 5 Geometry

In parallelogram ABCD, angle ADC = (3x + 12)° and angle ABC = (x + 48)°. Find angle DAB.

A 114°
B 66°
C 48°
D 132°
Show Worked Solution

Worked Solution

Step 1: In a parallelogram, opposite angles are equal. Angles ADC and ABC are opposite, so 3x + 12 = x + 48. Step 2: Solve for x: 3x − x = 48 − 12 → 2x = 36 → x = 18. Step 3: Angle ABC = 18 + 48 = 66°. Step 4: Angle DAB and angle ABC are co-interior (consecutive) angles, so they sum to 180°: angle DAB = 180° − 66° = 114°. Answer: 114°

Correct answer: 114°

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