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Year 9 Circumference and Area of Circles Worksheet — Level 3 — Practice Set 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 — Practice Set 3 — Answers

Show your working. Use the π button on your calculator and round to 1 decimal place unless told otherwise.

1.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
2.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
3.A circle has a diameter of 18 cm. Find its area, correct to 1 decimal place.

Answer: 254.5 cm2

  1. r = 18 ÷ 2 = 9 cm
  2. A = π × r2 = π × 92 = π × 81
  3. ≈ 254.5 cm2
4.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
5.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
6.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
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 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
9.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
10.A circle has a circumference of 6π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 3 cm; A = 9π cm2

  1. C = 2πr, so 2πr = 6π
  2. r = 3 cm
  3. A = πr2 = 9π cm2
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