Let's solve each problem step by step.
We are given the
diameter of each circle, and we need to calculate:
-
Circumference = $ C = \pi \times d $ or $ C = 2\pi r $
-
Area = $ A = \pi r^2 $
Since the diameter is given, we can find the radius:
$ r = \frac{d}{2} $
We'll use $ \pi \approx 3.14 $ for calculations.
---
1. Diameter = 16 cm
- Radius $ r = \frac{16}{2} = 8 $ cm
- Circumference:
$ C = \pi \times d = 3.14 \times 16 = 50.24 $ cm
- Area:
$ A = \pi r^2 = 3.14 \times 8^2 = 3.14 \times 64 = 200.96 $ cm²
✔ Circumference: 50.24 cm,
Area: 200.96 cm²
---
2. Diameter = 20 cm
- Radius $ r = \frac{20}{2} = 10 $ cm
- Circumference:
$ C = 3.14 \times 20 = 62.8 $ cm
- Area:
$ A = 3.14 \times 10^2 = 3.14 \times 100 = 314 $ cm²
✔ Circumference: 62.8 cm,
Area: 314 cm²
---
3. Diameter = 10 cm
- Radius $ r = \frac{10}{2} = 5 $ cm
- Circumference:
$ C = 3.14 \times 10 = 31.4 $ cm
- Area:
$ A = 3.14 \times 5^2 = 3.14 \times 25 = 78.5 $ cm²
✔ Circumference: 31.4 cm,
Area: 78.5 cm²
---
4. Diameter = 8 cm
- Radius $ r = \frac{8}{2} = 4 $ cm
- Circumference:
$ C = 3.14 \times 8 = 25.12 $ cm
- Area:
$ A = 3.14 \times 4^2 = 3.14 \times 16 = 50.24 $ cm²
✔ Circumference: 25.12 cm,
Area: 50.24 cm²
---
5. Diameter = 18 cm
- Radius $ r = \frac{18}{2} = 9 $ cm
- Circumference:
$ C = 3.14 \times 18 = 56.52 $ cm
- Area:
$ A = 3.14 \times 9^2 = 3.14 \times 81 = 254.34 $ cm²
✔ Circumference: 56.52 cm,
Area: 254.34 cm²
---
6. Diameter = 11 cm
- Radius $ r = \frac{11}{2} = 5.5 $ cm
- Circumference:
$ C = 3.14 \times 11 = 34.54 $ cm
- Area:
$ A = 3.14 \times (5.5)^2 = 3.14 \times 30.25 = 95.03 $ cm²
✔ Circumference: 34.54 cm,
Area: 95.03 cm²
---
✔ Final Answers:
| Number | Circumference | Area |
|--------|----------------|--------------|
| 1 | 50.24 cm | 200.96 cm² |
| 2 | 62.8 cm | 314 cm² |
| 3 | 31.4 cm | 78.5 cm² |
| 4 | 25.12 cm | 50.24 cm² |
| 5 | 56.52 cm | 254.34 cm² |
| 6 | 34.54 cm | 95.03 cm² |
> 🔍
Note: All values rounded to two decimal places using $ \pi \approx 3.14 $. If more precision is needed, you can use $ \pi \approx 3.1416 $, but this is standard for school-level problems.
Let me know if you'd like these answers written in a specific format!
Parent Tip: Review the logic above to help your child master the concept of math worksheet grade 7.
