To solve this worksheet, we need to
find the circumference of each circle using the given radius or diameter. The formula for the
circumference (C) of a circle is:
$$
C = 2\pi r \quad \text{or} \quad C = \pi d
$$
Where:
- $ r $ is the
radius
- $ d $ is the
diameter
- $ \pi \approx 3.14 $
We'll use $ \pi \approx 3.14 $ unless otherwise specified.
Let’s go through each problem one by one.
---
1) Radius = 13.5 cm
$$
C = 2\pi r = 2 \times 3.14 \times 13.5 = 6.28 \times 13.5 = 84.78 \text{ cm}
$$
✔ Answer: 84.78 cm
---
2) Radius = 13 cm
$$
C = 2 \times 3.14 \times 13 = 6.28 \times 13 = 81.64 \text{ cm}
$$
✔ Answer: 81.64 cm
---
3) Radius = 2 cm
$$
C = 2 \times 3.14 \times 2 = 6.28 \times 2 = 12.56 \text{ cm}
$$
✔ Answer: 12.56 cm
---
4) Diameter = 19 cm
Use $ C = \pi d $
$$
C = 3.14 \times 19 = 59.66 \text{ cm}
$$
✔ Answer: 59.66 cm
---
5) Radius = 11 cm
$$
C = 2 \times 3.14 \times 11 = 6.28 \times 11 = 69.08 \text{ cm}
$$
✔ Answer: 69.08 cm
---
6) Diameter = 16 cm
$$
C = 3.14 \times 16 = 50.24 \text{ cm}
$$
✔ Answer: 50.24 cm
---
7) Diameter = 2 cm
$$
C = 3.14 \times 2 = 6.28 \text{ cm}
$$
✔ Answer: 6.28 cm
---
8) Radius = 7.5 cm
$$
C = 2 \times 3.14 \times 7.5 = 6.28 \times 7.5 = 47.1 \text{ cm}
$$
✔ Answer: 47.1 cm
---
9) Radius = 6.5 cm
$$
C = 2 \times 3.14 \times 6.5 = 6.28 \times 6.5 = 40.82 \text{ cm}
$$
✔ Answer: 40.82 cm
---
10) Radius = 2.5 cm
$$
C = 2 \times 3.14 \times 2.5 = 6.28 \times 2.5 = 15.7 \text{ cm}
$$
✔ Answer: 15.7 cm
---
✔ Final Answers:
| Problem | Circumference (cm) |
|--------|---------------------|
| 1 | 84.78 |
| 2 | 81.64 |
| 3 | 12.56 |
| 4 | 59.66 |
| 5 | 69.08 |
| 6 | 50.24 |
| 7 | 6.28 |
| 8 | 47.1 |
| 9 | 40.82 |
| 10 | 15.7 |
---
🔍 Explanation Summary:
- For
radius, use $ C = 2\pi r $
- For
diameter, use $ C = \pi d $
- Always multiply by $ \pi \approx 3.14 $
- Units are in
centimeters (cm) as specified
Let me know if you'd like this formatted for printing or want answers rounded differently!
Parent Tip: Review the logic above to help your child master the concept of circle circumference worksheet answers.
