Lessons · Quantitative Reasoning
CLT Quantitative Reasoning · Lesson
Angles and polygons
Angles on a straight line add to 180°, around a point to 360°. A polygon with n sides has interior angles that add to (n − 2) × 180°.
- Mark every angle you know on the figure, including the ones you can work out.
- Use parallel lines: corresponding and alternate angles are equal.
- For a regular polygon, divide the interior sum by n. The exterior angles always add to 360°.
Q. What is each interior angle of a regular hexagon?
Answer 120°
(6 − 2) × 180° = 720°, and 720° ÷ 6 = 120°. Or: each exterior angle is 360° ÷ 6 = 60°, and 180° − 60° = 120°.
- Using n × 180° instead of (n − 2) × 180°.
- Assuming a figure is drawn to scale. Use the given numbers, not the picture.
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