Math worksheet for calculating the area of circles using diameter and radius measurements.

Let's solve each of these circle area problems step by step using the formula for the area of a circle:

$$
A = \pi r^2
$$

Where:
- $ A $ is the area,
- $ r $ is the radius,
- $ \pi \approx 3.14 $ (we'll use this approximation unless otherwise specified),
- If given diameter, remember: $ r = \frac{d}{2} $

We’ll calculate each area and round to 1 decimal place (1dp) as instructed.

---

1) Diameter = 5 cm

- Radius $ r = \frac{5}{2} = 2.5 $ cm
- $ A = \pi \times (2.5)^2 = 3.14 \times 6.25 = 19.625 $
- $ \boxed{A = 19.6} $ cm²

---

2) Radius = 3 m

- $ A = \pi \times (3)^2 = 3.14 \times 9 = 28.26 $
- $ \boxed{A = 28.3} $ m²

---

3) Diameter = 8 mm

- Radius $ r = \frac{8}{2} = 4 $ mm
- $ A = \pi \times (4)^2 = 3.14 \times 16 = 50.24 $
- $ \boxed{A = 50.2} $ mm²

---

4) Radius = 1.5 m

- $ A = \pi \times (1.5)^2 = 3.14 \times 2.25 = 7.065 $
- $ \boxed{A = 7.1} $ m²

---

5) Diameter = 11 cm

- Radius $ r = \frac{11}{2} = 5.5 $ cm
- $ A = \pi \times (5.5)^2 = 3.14 \times 30.25 = 94.985 $
- $ \boxed{A = 95.0} $ cm²

---

6) Radius = 7 mm

- $ A = \pi \times (7)^2 = 3.14 \times 49 = 153.86 $
- $ \boxed{A = 153.9} $ mm²

---

7) Diameter = 17 cm

- Radius $ r = \frac{17}{2} = 8.5 $ cm
- $ A = \pi \times (8.5)^2 = 3.14 \times 72.25 = 226.57 $
- $ \boxed{A = 226.6} $ cm²

---

8) Radius = 9 mm

- $ A = \pi \times (9)^2 = 3.14 \times 81 = 254.34 $
- $ \boxed{A = 254.3} $ mm²

---

9) Diameter = 9 m

- Radius $ r = \frac{9}{2} = 4.5 $ m
- $ A = \pi \times (4.5)^2 = 3.14 \times 20.25 = 63.585 $
- $ \boxed{A = 63.6} $ m²

---

10) Diameter = 13 cm

- Radius $ r = \frac{13}{2} = 6.5 $ cm
- $ A = \pi \times (6.5)^2 = 3.14 \times 42.25 = 132.665 $
- $ \boxed{A = 132.7} $ cm²

---

11) Diameter = 15 mm

- Radius $ r = \frac{15}{2} = 7.5 $ mm
- $ A = \pi \times (7.5)^2 = 3.14 \times 56.25 = 176.625 $
- $ \boxed{A = 176.6} $ mm²

---

12) Radius = 6½ cm = 6.5 cm

- $ A = \pi \times (6.5)^2 = 3.14 \times 42.25 = 132.665 $
- $ \boxed{A = 132.7} $ cm²

---

✔ Final Answers:

| Problem | Area (to 1dp) |
|--------|----------------|
| 1) | 19.6 cm² |
| 2) | 28.3 m² |
| 3) | 50.2 mm² |
| 4) | 7.1 m² |
| 5) | 95.0 cm² |
| 6) | 153.9 mm² |
| 7) | 226.6 cm² |
| 8) | 254.3 mm² |
| 9) | 63.6 m² |
| 10) | 132.7 cm² |
| 11) | 176.6 mm² |
| 12) | 132.7 cm² |

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🔍 Summary Notes:

- Always check if you're given radius or diameter.
- Use $ r = \frac{d}{2} $ when diameter is given.
- Use $ A = \pi r^2 $, with $ \pi \approx 3.14 $.
- Round your final answer to 1 decimal place.

Let me know if you'd like this in a printable format or need help understanding any specific problem!