8th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 2 — Answers
Answer sheet with worked solutions for the 8th Grade area & perimeter worksheet.
Success TutoringWorksheetsAnswer sheet8th Grade · Mathematics · Area & Perimeter8th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 2 — Answers
Show your work. Use the π button on your calculator and round to 1 decimal place unless told otherwise.
1.Find the area of a semicircle with a radius of 20 cm, correct to 1 decimal place.
Answer: 628.3 cm2
- A = ½ × π × r2 = ½ × π × 400
- ≈ 628.3 cm2
2.A circle has a circumference of 24π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 12 cm; A = 144π cm2
- C = 2πr, so 2πr = 24π
- r = 12 cm
- A = πr2 = 144π cm2
3.A circle has a radius of 7 cm. Find its area, correct to 1 decimal place.
Answer: 153.9 cm2
- A = π × r2 = π × 72 = π × 49
- ≈ 153.9 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 circumference of 38π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 19 cm; A = 361π cm2
- C = 2πr, so 2πr = 38π
- r = 19 cm
- A = πr2 = 361π cm2
6.A circle has a diameter of 10 cm. Find its area, correct to 1 decimal place.
Answer: 78.5 cm2
- r = 10 ÷ 2 = 5 cm
- A = π × r2 = π × 52 = π × 25
- ≈ 78.5 cm2
7.A circle has a circumference of 26π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 13 cm; A = 169π cm2
- C = 2πr, so 2πr = 26π
- r = 13 cm
- A = πr2 = 169π cm2
8.A circle has a diameter of 12 cm. Find its area, correct to 1 decimal place.
Answer: 113.1 cm2
- r = 12 ÷ 2 = 6 cm
- A = π × r2 = π × 62 = π × 36
- ≈ 113.1 cm2
9.A circle has a diameter of 28 cm. Find its area, correct to 1 decimal place.
Answer: 615.8 cm2
- r = 28 ÷ 2 = 14 cm
- A = π × r2 = π × 142 = π × 196
- ≈ 615.8 cm2
10.A circle has a circumference of 14π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 7 cm; A = 49π cm2
- C = 2πr, so 2πr = 14π
- r = 7 cm
- A = πr2 = 49π 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.