8th Grade Circumference and Area of Circles Worksheet — Level 3 — Answers
Answer sheet with worked solutions for the 8th Grade area & perimeter worksheet.
Success TutoringWorksheetsAnswer sheet8th Grade · Mathematics · Area & Perimeter8th Grade Circumference and Area of Circles Worksheet — Level 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 circumference of 28π cm. Find its radius and its area (leave the area in terms of π).
Answer: r = 14 cm; A = 196π cm2
- C = 2πr, so 2πr = 28π
- r = 14 cm
- A = πr2 = 196π cm2
2.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
- C = 2πr, so 2πr = 24π
- r = 12 cm
- A = πr2 = 144π cm2
3.Find the area of a semicircle with a radius of 20 cm, correct to 1 decimal place.
Answer: 628.3 cm2
- A = ½ × π × r2 = ½ × π × 400
- ≈ 628.3 cm2
4.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
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 7 cm. Find its area, correct to 1 decimal place.
Answer: 153.9 cm2
- A = π × r2 = π × 72 = π × 49
- ≈ 153.9 cm2
7.A circle has a diameter of 40 cm. Find its area, correct to 1 decimal place.
Answer: 1256.6 cm2
- r = 40 ÷ 2 = 20 cm
- A = π × r2 = π × 202 = π × 400
- ≈ 1256.6 cm2
8.Find the area of a semicircle with a radius of 16 cm, correct to 1 decimal place.
Answer: 402.1 cm2
- A = ½ × π × r2 = ½ × π × 256
- ≈ 402.1 cm2
9.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
- C = 2πr, so 2πr = 10π
- r = 5 cm
- A = πr2 = 25π cm2
10.A circle has a radius of 10 cm. Find its area, correct to 1 decimal place.
Answer: 314.2 cm2
- A = π × r2 = π × 102 = π × 100
- ≈ 314.2 cm2
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