Year 9 Angles in Polygons Worksheet — Level 2 — Practice Set 3 — Answers
Answer sheet with worked solutions for the Year 9 angles worksheet.
Success TutoringWorksheetsAnswer sheetYear 9 · Mathematics · AnglesYear 9 Angles in Polygons Worksheet — Level 2 — Practice Set 3 — 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 decagon.
Answer: 1,440°
- Angle sum = (n − 2) × 180°
- (10 − 2) × 180° = 1,440°
2.Find the size of each interior angle of a regular octagon.
Answer: 135°
- Angle sum = (8 − 2) × 180° = 1,080°
- 1,080° ÷ 8 = 135°
3.Find the size of each exterior angle of a regular 15-sided polygon.
Answer: 24°
- Exterior angles add to 360°
- 360° ÷ 15 = 24°
4.Each exterior angle of a regular polygon is 45°. How many sides does it have?
Answer: 8
- Exterior angles add to 360°
- 360 ÷ 45 = 8 sides
5.Find the sum of the interior angles of an octagon.
Answer: 1,080°
- Angle sum = (n − 2) × 180°
- (8 − 2) × 180° = 1,080°
6.Find the size of each interior angle of a regular triangle.
Answer: 60°
- Angle sum = (3 − 2) × 180° = 180°
- 180° ÷ 3 = 60°
7.Find the size of each exterior angle of a regular hexagon.
Answer: 60°
- Exterior angles add to 360°
- 360° ÷ 6 = 60°
8.Each exterior angle of a regular polygon is 15°. How many sides does it have?
Answer: 24
- Exterior angles add to 360°
- 360 ÷ 15 = 24 sides
9.Find the sum of the interior angles of a heptagon.
Answer: 900°
- Angle sum = (n − 2) × 180°
- (7 − 2) × 180° = 900°
10.Find the size of each interior angle of a regular quadrilateral.
Answer: 90°
- Angle sum = (4 − 2) × 180° = 360°
- 360° ÷ 4 = 90°
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