Math worksheet for calculating the area and circumference of circles.

Let's solve each problem step by step using the formulas for area and circumference of a circle:

🔷 Formulas:

- Diameter (d) = 2 × Radius (r)
- Radius (r) = Diameter ÷ 2
- Area (A) = π × r²
- Circumference (C) = 2π × r or π × d

We’ll use π ≈ 3.14 unless otherwise specified.

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Problem 1

- Given: Radius = 4 ft
- Diameter = 2 × 4 = 8 ft
- Area = π × r² = π × 4² = π × 16 = 16π ft²
- Circumference = 2π × r = 2π × 4 = 8π ft

✔ Answer:
- Radius = 4 ft
- Diameter = 8 ft
- Area = 16π ft²
- Circumference = 8π ft

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Problem 2

- Given: Radius = 7 cm
- Diameter = 2 × 7 = 14 cm
- Area = π × 7² = π × 49 = 49π cm²
- Circumference = 2π × 7 = 14π cm

✔ Answer:
- Radius = 7 cm
- Diameter = 14 cm
- Area = 49π cm²
- Circumference = 14π cm

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Problem 3

- Given: Diameter = 14 m
- Radius = 14 ÷ 2 = 7 m
- Area = π × 7² = 49π m²
- Circumference = π × 14 = 14π m

✔ Answer:
- Radius = 7 m
- Diameter = 14 m
- Area = 49π m²
- Circumference = 14π m

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Problem 4

- Given: Radius = 9 in
- Diameter = 2 × 9 = 18 in
- Area = π × 9² = π × 81 = 81π in²
- Circumference = 2π × 9 = 18π in

✔ Answer:
- Radius = 9 in
- Diameter = 18 in
- Area = 81π in²
- Circumference = 18π in

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Problem 5

- Given: Diameter = 36 ft
- Radius = 36 ÷ 2 = 18 ft
- Area = π × 18² = π × 324 = 324π ft²
- Circumference = π × 36 = 36π ft

✔ Answer:
- Radius = 18 ft
- Diameter = 36 ft
- Area = 324π ft²
- Circumference = 36π ft

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Problem 6

- Given: Radius = 5 in
- Diameter = 2 × 5 = 10 in
- Area = π × 5² = π × 25 = 25π in²
- Circumference = 2π × 5 = 10π in

✔ Answer:
- Radius = 5 in
- Diameter = 10 in
- Area = 25π in²
- Circumference = 10π in

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Problem 7

- Given: Diameter = 30 cm
- Radius = 30 ÷ 2 = 15 cm
- Area = π × 15² = π × 225 = 225π cm²
- Circumference = π × 30 = 30π cm

✔ Answer:
- Radius = 15 cm
- Diameter = 30 cm
- Area = 225π cm²
- Circumference = 30π cm

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Problem 8

- Given: Radius = 8 mm
- Diameter = 2 × 8 = 16 mm
- Area = π × 8² = π × 64 = 64π mm²
- Circumference = 2π × 8 = 16π mm

✔ Answer:
- Radius = 8 mm
- Diameter = 16 mm
- Area = 64π mm²
- Circumference = 16π mm

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Problem 9

- Given: Diameter = 25 km
- Radius = 25 ÷ 2 = 12.5 km
- Area = π × (12.5)² = π × 156.25 = 156.25π km²
- Circumference = π × 25 = 25π km

✔ Answer:
- Radius = 12.5 km
- Diameter = 25 km
- Area = 156.25π km²
- Circumference = 25π km

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✔ Final Answers Summary:

| # | Radius | Diameter | Area | Circumference |
|---|--------|----------|------------|----------------|
| 1 | 4 ft | 8 ft | 16π ft² | 8π ft |
| 2 | 7 cm | 14 cm | 49π cm² | 14π cm |
| 3 | 7 m | 14 m | 49π m² | 14π m |
| 4 | 9 in | 18 in | 81π in² | 18π in |
| 5 | 18 ft | 36 ft | 324π ft² | 36π ft |
| 6 | 5 in | 10 in | 25π in² | 10π in |
| 7 | 15 cm | 30 cm | 225π cm² | 30π cm |
| 8 | 8 mm | 16 mm | 64π mm² | 16π mm |
| 9 | 12.5 km| 25 km | 156.25π km²| 25π km |

> 💡 Note: The question asks for exact area and circumference, so we leave answers in terms of π, not decimal approximations.

Let me know if you'd like decimal versions too!