Standard Mathematics Primary 5 Angles

Three rays from point O divide the full angle at O into three parts: angle AOB = 2n°, angle BOC = (3n + 10)° and angle COA = (n + 50)°. Find the value of n.

A 40
B 45
C 50
D 60
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Worked Solution

Step 1: Angles at a point sum to 360°. Step 2: Write the equation: 2n + (3n + 10) + (n + 50) = 360. Step 3: Collect n-terms: 2n + 3n + n = 6n. Collect constants: 10 + 50 = 60. Simplified: 6n + 60 = 360. Step 4: Isolate 6n: 6n = 360 − 60 = 300. Step 5: Solve: n = 300 ÷ 6 = 50. Verify: 2(50) + (3×50+10) + (50+50) = 100 + 160 + 100 = 360°. ✓ Answer: 50

Correct answer: 50

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