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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 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
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.Find the area of a semicircle with a radius of 17 cm, correct to 1 decimal place.

Answer: 454.0 cm2

  1. A = ½ × π × r2 = ½ × π × 289
  2. ≈ 454.0 cm2
4.A circle has a diameter of 32 cm. Find its area, correct to 1 decimal place.

Answer: 804.2 cm2

  1. r = 32 ÷ 2 = 16 cm
  2. A = π × r2 = π × 162 = π × 256
  3. ≈ 804.2 cm2
5.A circle has a radius of 10 cm. Find its area, correct to 1 decimal place.

Answer: 314.2 cm2

  1. A = π × r2 = π × 102 = π × 100
  2. ≈ 314.2 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.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
8.A circle has a circumference of 4π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 2 cm; A = 4π cm2

  1. C = 2πr, so 2πr = 4π
  2. r = 2 cm
  3. A = πr2 = 4π cm2
9.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
10.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
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