Year 8 Angles in Polygons Worksheet — Level 2 — Practice Set 2 — Answers
Answer sheet with worked solutions for the Year 8 angles worksheet.
Success TutoringWorksheetsAnswer sheetYear 8 · Mathematics · AnglesYear 8 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 triangle.
Answer: 60°
- Angle sum = (3 − 2) × 180° = 180°
- 180° ÷ 3 = 60°
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 10°. How many sides does it have?
Answer: 36
- Exterior angles add to 360°
- 360 ÷ 10 = 36 sides
5.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°
6.Find the size of each interior angle of a regular pentagon.
Answer: 108°
- Angle sum = (5 − 2) × 180° = 540°
- 540° ÷ 5 = 108°
7.Find the size of each exterior angle of a regular 20-sided polygon.
Answer: 18°
- Exterior angles add to 360°
- 360° ÷ 20 = 18°
8.Each exterior angle of a regular polygon is 40°. How many sides does it have?
Answer: 9
- Exterior angles add to 360°
- 360 ÷ 40 = 9 sides
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 15-sided polygon.
Answer: 156°
- Angle sum = (15 − 2) × 180° = 2,340°
- 2,340° ÷ 15 = 156°
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.
Great work. Here's what to try next: