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Year 9 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 2 — 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 2 — 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 40π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 20 cm; A = 400π cm2

  1. C = 2πr, so 2πr = 40π
  2. r = 20 cm
  3. A = πr2 = 400π cm2
2.Find the area of a semicircle with a radius of 7 cm, correct to 1 decimal place.

Answer: 77.0 cm2

  1. A = ½ × π × r2 = ½ × π × 49
  2. ≈ 77.0 cm2
3.Find the area of a semicircle with a radius of 10 cm, correct to 1 decimal place.

Answer: 157.1 cm2

  1. A = ½ × π × r2 = ½ × π × 100
  2. ≈ 157.1 cm2
4.A circle has a radius of 9 cm. Find its area, correct to 1 decimal place.

Answer: 254.5 cm2

  1. A = π × r2 = π × 92 = π × 81
  2. ≈ 254.5 cm2
5.A circle has a circumference of 30π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 15 cm; A = 225π cm2

  1. C = 2πr, so 2πr = 30π
  2. r = 15 cm
  3. A = πr2 = 225π cm2
6.Find the area of a semicircle with a radius of 3 cm, correct to 1 decimal place.

Answer: 14.1 cm2

  1. A = ½ × π × r2 = ½ × π × 9
  2. ≈ 14.1 cm2
7.A circle has a radius of 17 cm. Find its area, correct to 1 decimal place.

Answer: 907.9 cm2

  1. A = π × r2 = π × 172 = π × 289
  2. ≈ 907.9 cm2
8.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
9.A circle has a circumference of 28π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 14 cm; A = 196π cm2

  1. C = 2πr, so 2πr = 28π
  2. r = 14 cm
  3. A = πr2 = 196π cm2
10.Find the area of a semicircle with a radius of 6 cm, correct to 1 decimal place.

Answer: 56.5 cm2

  1. A = ½ × π × r2 = ½ × π × 36
  2. ≈ 56.5 cm2
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