Let's solve each circle problem step by step using the formulas for
radius,
diameter, and
circumference.
🔷 Key Formulas:
-
Diameter (d) = 2 × Radius (r)
-
Radius (r) = Diameter ÷ 2
-
Circumference (C) = π × d or 2π × r
(Use π ≈ 3.14 as instructed)
---
🔹 Circle 1: Radius = 7 cm
Given: Radius = 7 cm
-
Radius = 7 cm
✔
-
Diameter = 2 × 7 =
14 cm
-
Circumference = 2 × π × r = 2 × 3.14 × 7 =
43.96 cm
>
✔ Answers:
> - Radius:
7 cm
> - Diameter:
14 cm
> - Circumference:
43.96 cm
---
🔹 Circle 2: Diameter = 11 m
Given: Diameter = 11 m
-
Radius = 11 ÷ 2 =
5.5 m
-
Diameter = 11 m
✔
-
Circumference = π × d = 3.14 × 11 =
34.54 m
>
✔ Answers:
> - Radius:
5.5 m
> - Diameter:
11 m
> - Circumference:
34.54 m
---
🔹 Circle 3: Diameter = 18 km
Given: Diameter = 18 km
-
Radius = 18 ÷ 2 =
9 km
-
Diameter = 18 km
✔
-
Circumference = π × d = 3.14 × 18 =
56.52 km
>
✔ Answers:
> - Radius:
9 km
> - Diameter:
18 km
> - Circumference:
56.52 km
---
🔹 Circle 4: Radius = 12 cm
Given: Radius = 12 cm
-
Radius = 12 cm
✔
-
Diameter = 2 × 12 =
24 cm
-
Circumference = 2 × π × r = 2 × 3.14 × 12 =
75.36 cm
>
✔ Answers:
> - Radius:
12 cm
> - Diameter:
24 cm
> - Circumference:
75.36 cm
---
✔ Final Answer Summary:
| Circle | Radius | Diameter | Circumference |
|--------|------------|------------|----------------|
| 1 | 7 cm | 14 cm | 43.96 cm |
| 2 | 5.5 m | 11 m | 34.54 m |
| 3 | 9 km | 18 km | 56.52 km |
| 4 | 12 cm | 24 cm | 75.36 cm |
---
💡 Tips:
- Always check whether you're given
radius or
diameter.
- Use
π ≈ 3.14 unless told otherwise.
- Units must be consistent (cm, m, km, etc.).
Let me know if you'd like this formatted into a printable answer sheet!
Parent Tip: Review the logic above to help your child master the concept of circumference word problems worksheet.
