Year 9 Angles in Polygons Worksheet — Level 1 — Answers
Answer sheet with worked solutions for the Year 9 angles worksheet.
Success TutoringWorksheetsAnswer sheetYear 9 · Mathematics · AnglesYear 9 Angles in Polygons Worksheet — Level 1 — Answers
Interior angle sum = (n − 2) × 180°. The exterior angles of any convex polygon add to 360°.
1.Find the sum of the interior angles of a 20-sided polygon.
Answer: 3,240°
- Angle sum = (n − 2) × 180°
- (20 − 2) × 180° = 3,240°
2.Find the size of each interior angle of a regular 30-sided polygon.
Answer: 168°
- Angle sum = (30 − 2) × 180° = 5,040°
- 5,040° ÷ 30 = 168°
3.Find the sum of the interior angles of a dodecagon.
Answer: 1,800°
- Angle sum = (n − 2) × 180°
- (12 − 2) × 180° = 1,800°
4.Find the size of each interior angle of a regular quadrilateral.
Answer: 90°
- Angle sum = (4 − 2) × 180° = 360°
- 360° ÷ 4 = 90°
5.Find the sum of the interior angles of a quadrilateral.
Answer: 360°
- Angle sum = (n − 2) × 180°
- (4 − 2) × 180° = 360°
6.Find the size of each interior angle of a regular dodecagon.
Answer: 150°
- Angle sum = (12 − 2) × 180° = 1,800°
- 1,800° ÷ 12 = 150°
7.Find the sum of the interior angles of a 14-sided polygon.
Answer: 2,160°
- Angle sum = (n − 2) × 180°
- (14 − 2) × 180° = 2,160°
8.Find the size of each interior angle of a regular pentagon.
Answer: 108°
- Angle sum = (5 − 2) × 180° = 540°
- 540° ÷ 5 = 108°
9.Find the sum of the interior angles of a pentagon.
Answer: 540°
- Angle sum = (n − 2) × 180°
- (5 − 2) × 180° = 540°
10.Find the size of each interior angle of a regular 18-sided polygon.
Answer: 160°
- Angle sum = (18 − 2) × 180° = 2,880°
- 2,880° ÷ 18 = 160°
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