Year 7 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — Answers
Answer sheet with worked solutions for the Year 7 area & perimeter worksheet.
Year 7 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — 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 circumference of 10π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 5 cm; A = 25π cm2
- C = 2πr, so 2πr = 10π
- r = 5 cm
- A = πr2 = 25π cm2
2.Find the area of a semicircle with a radius of 7 cm, correct to 1 decimal place.
Answer: 77.0 cm2
- A = ½ × π × r2 = ½ × π × 49
- ≈ 77.0 cm2
3.A circle has a radius of 6 cm. Find its area, correct to 1 decimal place.
Answer: 113.1 cm2
- A = π × r2 = π × 62 = π × 36
- ≈ 113.1 cm2
4.A circle has a circumference of 36π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 18 cm; A = 324π cm2
- C = 2πr, so 2πr = 36π
- r = 18 cm
- A = πr2 = 324π cm2
5.A circle has a radius of 18 cm. Find its area, correct to 1 decimal place.
Answer: 1017.9 cm2
- A = π × r2 = π × 182 = π × 324
- ≈ 1017.9 cm2
6.A circle has a radius of 2 cm. Find its area, correct to 1 decimal place.
Answer: 12.6 cm2
- A = π × r2 = π × 22 = π × 4
- ≈ 12.6 cm2
7.A circle has a circumference of 4π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 2 cm; A = 4π cm2
- C = 2πr, so 2πr = 4π
- r = 2 cm
- A = πr2 = 4π cm2
8.Find the area of a semicircle with a radius of 15 cm, correct to 1 decimal place.
Answer: 353.4 cm2
- A = ½ × π × r2 = ½ × π × 225
- ≈ 353.4 cm2
9.A circle has a circumference of 16π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 8 cm; A = 64π cm2
- C = 2πr, so 2πr = 16π
- r = 8 cm
- A = πr2 = 64π cm2
10.A circle has a radius of 9 cm. Find its area, correct to 1 decimal place.
Answer: 254.5 cm2
- A = π × r2 = π × 92 = π × 81
- ≈ 254.5 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.