Geometry & MeasuresStudy Notes

Common Mistakes

Part of Angles in Polygons · GCSE GCSE Mathematics revision

This study notes covers Common Mistakes within Angles in Polygons for GCSE Mathematics. Revise Angles in Polygons in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 8 of 10 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 8 of 10

Practice

12 questions

Recall

3 flashcards

Common Mistakes

✗ Wrong: Using (n) × 180° instead of (n − 2) × 180°

✓ Right: Always subtract 2 from the number of sides first

✗ Wrong: Interior angle = 360° ÷ n

✓ Right: That's the EXTERIOR angle! Interior = 180° − (360° ÷ n)

✗ Wrong: Sum of exterior angles = (n − 2) × 180°

✓ Right: Exterior angles ALWAYS sum to 360° (any polygon!)

Keep building this topic

Read this section alongside the surrounding pages in Angles in Polygons. That gives you the full topic sequence instead of a single isolated revision point.

Worked Example 4: Missing Angle in Irregular Polygon Practice Questions The Triangle Trick Essential Formulas

Practice Questions for Angles in Polygons

What is the sum of the interior angles of a hexagon?

A. 540°
B. 720°
C. 900°
D. 360°

1 markfoundation

Explain how the formula (n − 2) × 180° for the sum of interior angles of a polygon is derived.

2 markshigher

Quick Recall Flashcards

Exterior Angle Sum

Always 360° for any polygon

Interior Angle Sum

Sum = (n - 2) × 180° for n-sided polygon

12 questions on Angles in Polygons — practise free

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Worked Example 4: Missing Angle in Irregular Polygon

Practice Questions