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Year 9 Circumference and Area of Circles Worksheet — Level 3 — 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 — 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 16π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 8 cm; A = 64π cm2

  1. C = 2πr, so 2πr = 16π
  2. r = 8 cm
  3. A = πr2 = 64π cm2
2.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
3.A circle has a circumference of 18π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 9 cm; A = 81π cm2

  1. C = 2πr, so 2πr = 18π
  2. r = 9 cm
  3. A = πr2 = 81π cm2
4.A circle has a diameter of 14 cm. Find its area, correct to 1 decimal place.

Answer: 153.9 cm2

  1. r = 14 ÷ 2 = 7 cm
  2. A = π × r2 = π × 72 = π × 49
  3. ≈ 153.9 cm2
5.A circle has a radius of 14 cm. Find its area, correct to 1 decimal place.

Answer: 615.8 cm2

  1. A = π × r2 = π × 142 = π × 196
  2. ≈ 615.8 cm2
6.Find the area of a semicircle with a radius of 9 cm, correct to 1 decimal place.

Answer: 127.2 cm2

  1. A = ½ × π × r2 = ½ × π × 81
  2. ≈ 127.2 cm2
7.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
8.A circle has a circumference of 12π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 6 cm; A = 36π cm2

  1. C = 2πr, so 2πr = 12π
  2. r = 6 cm
  3. A = πr2 = 36π cm2
9.A circle has a diameter of 22 cm. Find its area, correct to 1 decimal place.

Answer: 380.1 cm2

  1. r = 22 ÷ 2 = 11 cm
  2. A = π × r2 = π × 112 = π × 121
  3. ≈ 380.1 cm2
10.A circle has a radius of 2 cm. Find its area, correct to 1 decimal place.

Answer: 12.6 cm2

  1. A = π × r2 = π × 22 = π × 4
  2. ≈ 12.6 cm2
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