Advanced Mathematics Primary 4 Angles

A student needs to draw a reflex angle of 240° using only a 180° protractor. What should the student draw first?

A 120°
B 60°
C 180°
D 240°
Show Worked Solution

Worked Solution

Step 1: A reflex angle is greater than 180°. 240° is a reflex angle. Step 2: A 180° protractor cannot measure reflex angles directly. Step 3: Non-reflex angle = 360° − 240° = 120°. Step 4: Draw the 120° angle using the protractor normally. Step 5: The reflex side (the larger region at the vertex) is the 240° angle. Step 6: Verify: 120° + 240° = 360°. ✓

Correct answer: 120°

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