HOTS Mathematics Primary 5 Angles

Ahmad is sawing a wooden plank along straight line PQ. At point O on the plank, he makes two saw cuts creating rays OA and OB on the same side of PQ. The exterior angle of triangle OAB at vertex B measures 117°, and angle BAO = 45°. Ahmad also notices that angle POA is exactly 3 times angle BOQ. What is angle BOQ?

A 18°
B 27°
C 36°
D 45°
Show Worked Solution

Worked Solution

Step 1: Find angle AOB using the exterior angle theorem. The exterior angle of a triangle equals the sum of the two non-adjacent interior angles. Exterior angle at B = angle BAO + angle AOB 117° = 45° + angle AOB angle AOB = 72° Step 2: Set up the straight-line angle equation. Let angle BOQ = x. Then angle POA = 3x. All three angles along straight line PQ sum to 180°: 3x + 72° + x = 180° 4x = 108° x = 27° Answer: angle BOQ = 27°.

Correct answer: 27°

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