Circumference of Circles Worksheet - Free Printable

Let’s solve each problem step by step.

We are told to use π = 3.14
Circumference formula:
→ If you have the diameter (d): Circumference = d × π
→ If you have the radius (r): Circumference = 2 × r × π

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Problem 1: Diameter = 18 cm
C = 18 × 3.14 = ?
18 × 3 = 54
18 × 0.14 = 2.52
Total = 54 + 2.52 = 56.52 cm

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Problem 2: Diameter = 24 mm
C = 24 × 3.14
24 × 3 = 72
24 × 0.14 = 3.36
Total = 72 + 3.36 = 75.36 mm

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Problem 3: Diameter = 16 ft
C = 16 × 3.14
16 × 3 = 48
16 × 0.14 = 2.24
Total = 48 + 2.24 = 50.24 ft

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Problem 4: Diameter = 84 miles
C = 84 × 3.14
Break it down:
80 × 3.14 = 251.2
4 × 3.14 = 12.56
Total = 251.2 + 12.56 = 263.76 miles

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Problem 5: Diameter = 123 m
C = 123 × 3.14
Do 100 × 3.14 = 314
20 × 3.14 = 62.8
3 × 3.14 = 9.42
Add them: 314 + 62.8 = 376.8; 376.8 + 9.42 = 386.22 m

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Problem 6: Radius = 4 cm → Diameter = 8 cm
C = 8 × 3.14 = 25.12 cm
OR using radius formula: 2 × 4 × 3.14 = 8 × 3.14 = 25.12 cm

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Problem 7: Radius = 36 mm → Diameter = 72 mm
C = 72 × 3.14
70 × 3.14 = 219.8
2 × 3.14 = 6.28
Total = 219.8 + 6.28 = 226.08 mm

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Problem 8: Radius = 21 ft → Diameter = 42 ft
C = 42 × 3.14
40 × 3.14 = 125.6
2 × 3.14 = 6.28
Total = 125.6 + 6.28 = 131.88 ft

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Problem 9: Radius = 56 miles → Diameter = 112 miles
C = 112 × 3.14
100 × 3.14 = 314
12 × 3.14 = 37.68
Total = 314 + 37.68 = 351.68 miles

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Problem 10: Radius = 90 m → Diameter = 180 m
C = 180 × 3.14
100 × 3.14 = 314
80 × 3.14 = 251.2
Total = 314 + 251.2 = 565.2 m

Wait — let me double-check that last one:

Actually, 180 × 3.14 is better done as:
180 × 3 = 540
180 × 0.14 = 25.2
Total = 540 + 25.2 = 565.2 m ✔

All calculations checked.

Final Answer:
1. 56.52 cm
2. 75.36 mm
3. 50.24 ft
4. 263.76 miles
5. 386.22 m
6. 25.12 cm
7. 226.08 mm
8. 131.88 ft
9. 351.68 miles
10. 565.2 m