Year 9 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 4 — Answers
Answer sheet with worked solutions for the Year 9 area & perimeter worksheet.
Success TutoringWorksheetsAnswer sheetYear 9 · Mathematics · Area & PerimeterYear 9 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 4 — Answers
Show your working. Use the π button on your calculator and round to 1 decimal place unless told otherwise.
1.A circle has a radius of 3 cm. Find its area, correct to 1 decimal place.
Answer: 28.3 cm2
- A = π × r2 = π × 32 = π × 9
- ≈ 28.3 cm2
2.Find the area of a semicircle with a radius of 4 cm, correct to 1 decimal place.
Answer: 25.1 cm2
- A = ½ × π × r2 = ½ × π × 16
- ≈ 25.1 cm2
3.A circle has a radius of 19 cm. Find its area, correct to 1 decimal place.
Answer: 1134.1 cm2
- A = π × r2 = π × 192 = π × 361
- ≈ 1134.1 cm2
4.A circle has a diameter of 38 cm. Find its area, correct to 1 decimal place.
Answer: 1134.1 cm2
- r = 38 ÷ 2 = 19 cm
- A = π × r2 = π × 192 = π × 361
- ≈ 1134.1 cm2
5.Find the area of a semicircle with a radius of 18 cm, correct to 1 decimal place.
Answer: 508.9 cm2
- A = ½ × π × r2 = ½ × π × 324
- ≈ 508.9 cm2
6.A circle has a circumference of 28π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 14 cm; A = 196π cm2
- C = 2πr, so 2πr = 28π
- r = 14 cm
- A = πr2 = 196π cm2
7.Find the area of a semicircle with a radius of 11 cm, correct to 1 decimal place.
Answer: 190.1 cm2
- A = ½ × π × r2 = ½ × π × 121
- ≈ 190.1 cm2
8.A circle has a diameter of 8 cm. Find its area, correct to 1 decimal place.
Answer: 50.3 cm2
- r = 8 ÷ 2 = 4 cm
- A = π × r2 = π × 42 = π × 16
- ≈ 50.3 cm2
9.Find the area of a semicircle with a radius of 9 cm, correct to 1 decimal place.
Answer: 127.2 cm2
- A = ½ × π × r2 = ½ × π × 81
- ≈ 127.2 cm2
10.A circle has a radius of 17 cm. Find its area, correct to 1 decimal place.
Answer: 907.9 cm2
- A = π × r2 = π × 172 = π × 289
- ≈ 907.9 cm2
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.