Year 9 Angles in Polygons Worksheet — Level 2 — Practice Set 2 — 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 2 — 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 20-sided polygon.
Answer: 162°
- Angle sum = (20 − 2) × 180° = 3,240°
- 3,240° ÷ 20 = 162°
3.Find the size of each exterior angle of a regular triangle.
Answer: 120°
- Exterior angles add to 360°
- 360° ÷ 3 = 120°
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 a 14-sided polygon.
Answer: 2,160°
- Angle sum = (n − 2) × 180°
- (14 − 2) × 180° = 2,160°
6.Find the size of each interior angle of a regular quadrilateral.
Answer: 90°
- Angle sum = (4 − 2) × 180° = 360°
- 360° ÷ 4 = 90°
7.Find the size of each exterior angle of a regular decagon.
Answer: 36°
- Exterior angles add to 360°
- 360° ÷ 10 = 36°
8.Each exterior angle of a regular polygon is 18°. How many sides does it have?
Answer: 20
- Exterior angles add to 360°
- 360 ÷ 18 = 20 sides
9.Find the sum of the interior angles of a 15-sided polygon.
Answer: 2,340°
- Angle sum = (n − 2) × 180°
- (15 − 2) × 180° = 2,340°
10.Find the size of each interior angle of a regular decagon.
Answer: 144°
- Angle sum = (10 − 2) × 180° = 1,440°
- 1,440° ÷ 10 = 144°
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