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Year 8 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 4 — 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 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 circumference of 14π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 7 cm; A = 49π cm2

  1. C = 2πr, so 2πr = 14π
  2. r = 7 cm
  3. A = πr2 = 49π cm2
2.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
3.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
4.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
5.Find the area of a semicircle with a radius of 20 cm, correct to 1 decimal place.

Answer: 628.3 cm2

  1. A = ½ × π × r2 = ½ × π × 400
  2. ≈ 628.3 cm2
6.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
7.A circle has a circumference of 8π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 4 cm; A = 16π cm2

  1. C = 2πr, so 2πr = 8π
  2. r = 4 cm
  3. A = πr2 = 16π cm2
8.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
9.Find the area of a semicircle with a radius of 13 cm, correct to 1 decimal place.

Answer: 265.5 cm2

  1. A = ½ × π × r2 = ½ × π × 169
  2. ≈ 265.5 cm2
10.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
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