Year 9 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — 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 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 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
2.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
3.Find the area of a semicircle with a radius of 3 cm, correct to 1 decimal place.
Answer: 14.1 cm2
- A = ½ × π × r2 = ½ × π × 9
- ≈ 14.1 cm2
4.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
5.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
6.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
7.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
8.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
9.A circle has a circumference of 20π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 10 cm; A = 100π cm2
- C = 2πr, so 2πr = 20π
- r = 10 cm
- A = πr2 = 100π cm2
10.A circle has a circumference of 34π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 17 cm; A = 289π cm2
- C = 2πr, so 2πr = 34π
- r = 17 cm
- A = πr2 = 289π cm2
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