9th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — Answers
Answer sheet with worked solutions for the 9th Grade area & perimeter worksheet.
Success TutoringWorksheetsAnswer sheet9th Grade · Mathematics · Area & Perimeter9th Grade Circumference and Area of Circles Worksheet — Level 3 — Practice Set 3 — 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 radius of 5 cm. Find its area, correct to 1 decimal place.
Answer: 78.5 cm2
- A = π × r2 = π × 52 = π × 25
- ≈ 78.5 cm2
2.A circle has a diameter of 32 cm. Find its area, correct to 1 decimal place.
Answer: 804.2 cm2
- r = 32 ÷ 2 = 16 cm
- A = π × r2 = π × 162 = π × 256
- ≈ 804.2 cm2
3.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
- C = 2πr, so 2πr = 32π
- r = 16 cm
- A = πr2 = 256π cm2
4.A circle has a radius of 9 cm. Find its area, correct to 1 decimal place.
Answer: 254.5 cm2
- A = π × r2 = π × 92 = π × 81
- ≈ 254.5 cm2
5.A circle has a radius of 11 cm. Find its area, correct to 1 decimal place.
Answer: 380.1 cm2
- A = π × r2 = π × 112 = π × 121
- ≈ 380.1 cm2
6.A circle has a radius of 19 cm. Find its area, correct to 1 decimal place.
Answer: 1134.1 cm2
- A = π × r2 = π × 192 = π × 361
- ≈ 1134.1 cm2
7.A circle has a circumference of 36π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 18 cm; A = 324π cm2
- C = 2πr, so 2πr = 36π
- r = 18 cm
- A = πr2 = 324π cm2
8.Find the area of a semicircle with a radius of 17 cm, correct to 1 decimal place.
Answer: 454.0 cm2
- A = ½ × π × r2 = ½ × π × 289
- ≈ 454.0 cm2
9.A circle has a radius of 7 cm. Find its area, correct to 1 decimal place.
Answer: 153.9 cm2
- A = π × r2 = π × 72 = π × 49
- ≈ 153.9 cm2
10.Find the area of a semicircle with a radius of 5 cm, correct to 1 decimal place.
Answer: 39.3 cm2
- A = ½ × π × r2 = ½ × π × 25
- ≈ 39.3 cm2
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