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Year 8 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — Answers

Answer sheet with worked solutions for the Year 8 area & perimeter worksheet.

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Success TutoringWorksheetsAnswer sheetYear 8 · Mathematics · Area & Perimeter

Year 8 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 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
2.A circle has a circumference of 22π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 11 cm; A = 121π cm2

  1. C = 2πr, so 2πr = 22π
  2. r = 11 cm
  3. A = πr2 = 121π cm2
3.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
4.A circle has a diameter of 24 cm. Find its area, correct to 1 decimal place.

Answer: 452.4 cm2

  1. r = 24 ÷ 2 = 12 cm
  2. A = π × r2 = π × 122 = π × 144
  3. ≈ 452.4 cm2
5.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
6.A circle has a radius of 13 cm. Find its area, correct to 1 decimal place.

Answer: 530.9 cm2

  1. A = π × r2 = π × 132 = π × 169
  2. ≈ 530.9 cm2
7.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

  1. C = 2πr, so 2πr = 10π
  2. r = 5 cm
  3. A = πr2 = 25π cm2
8.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
9.Find the area of a semicircle with a radius of 11 cm, correct to 1 decimal place.

Answer: 190.1 cm2

  1. A = ½ × π × r2 = ½ × π × 121
  2. ≈ 190.1 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

  1. C = 2πr, so 2πr = 34π
  2. r = 17 cm
  3. A = πr2 = 289π cm2
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