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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.

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Success TutoringWorksheetsAnswer sheetYear 9 · Mathematics · Area & Perimeter

Year 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 diameter of 6 cm. Find its area, correct to 1 decimal place.

Answer: 28.3 cm2

  1. r = 6 ÷ 2 = 3 cm
  2. A = π × r2 = π × 32 = π × 9
  3. ≈ 28.3 cm2
2.Find the area of a semicircle with a radius of 19 cm, correct to 1 decimal place.

Answer: 567.1 cm2

  1. A = ½ × π × r2 = ½ × π × 361
  2. ≈ 567.1 cm2
3.A circle has a circumference of 32π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 16 cm; A = 256π cm2

  1. C = 2πr, so 2πr = 32π
  2. r = 16 cm
  3. A = πr2 = 256π 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

  1. C = 2πr, so 2πr = 4π
  2. r = 2 cm
  3. A = πr2 = 4π cm2
5.Find the area of a semicircle with a radius of 8 cm, correct to 1 decimal place.

Answer: 100.5 cm2

  1. A = ½ × π × r2 = ½ × π × 64
  2. ≈ 100.5 cm2
6.Find the area of a semicircle with a radius of 14 cm, correct to 1 decimal place.

Answer: 307.9 cm2

  1. A = ½ × π × r2 = ½ × π × 196
  2. ≈ 307.9 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

  1. C = 2πr, so 2πr = 24π
  2. r = 12 cm
  3. A = πr2 = 144π cm2
8.Find the area of a semicircle with a radius of 12 cm, correct to 1 decimal place.

Answer: 226.2 cm2

  1. A = ½ × π × r2 = ½ × π × 144
  2. ≈ 226.2 cm2
9.A circle has a radius of 11 cm. Find its area, correct to 1 decimal place.

Answer: 380.1 cm2

  1. A = π × r2 = π × 112 = π × 121
  2. ≈ 380.1 cm2
10.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

  1. C = 2πr, so 2πr = 20π
  2. r = 10 cm
  3. A = πr2 = 100π cm2
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