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7th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 4 — Answers

Answer sheet with worked solutions for the 7th Grade area & perimeter worksheet.

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Success TutoringWorksheetsAnswer sheet7th Grade · Mathematics · Area & Perimeter

7th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 4 — Answers

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

1.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
2.Find the area of a semicircle with a radius of 2 cm, correct to 1 decimal place.

Answer: 6.3 cm2

  1. A = ½ × π × r2 = ½ × π × 4
  2. ≈ 6.3 cm2
3.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
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.Find the area of a semicircle with a radius of 15 cm, correct to 1 decimal place.

Answer: 353.4 cm2

  1. A = ½ × π × r2 = ½ × π × 225
  2. ≈ 353.4 cm2
6.Find the area of a semicircle with a radius of 16 cm, correct to 1 decimal place.

Answer: 402.1 cm2

  1. A = ½ × π × r2 = ½ × π × 256
  2. ≈ 402.1 cm2
7.A circle has a radius of 18 cm. Find its area, correct to 1 decimal place.

Answer: 1017.9 cm2

  1. A = π × r2 = π × 182 = π × 324
  2. ≈ 1017.9 cm2
8.A circle has a circumference of 12π cm. Find its radius and its area (leave the area in terms of π).

Answer: r = 6 cm; A = 36π cm2

  1. C = 2πr, so 2πr = 12π
  2. r = 6 cm
  3. A = πr2 = 36π 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 diameter of 20 cm. Find its area, correct to 1 decimal place.

Answer: 314.2 cm2

  1. r = 20 ÷ 2 = 10 cm
  2. A = π × r2 = π × 102 = π × 100
  3. ≈ 314.2 cm2
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