Find the area of a circle whose radius is :
(i) 2.8 m
(ii) 8.4 m

Answer

To find the area of a circle, we use the formula:

\[ \text{Area} = \pi r^2 \]

where \( r \) is the radius of the circle.

### Part (i): Radius = 2.8 m

1. **Identify the radius**:
- The radius \( r = 2.8 \) m.

2. **Substitute the radius into the area formula**:
\[ \text{Area} = \pi (2.8)^2 \]

3. **Calculate \( (2.8)^2 \)**:
\[ (2.8)^2 = 2.8 \times 2.8 = 7.84 \]

4. **Substitute \( (2.8)^2 \) back into the area formula**:
\[ \text{Area} = \pi \times 7.84 \]

5. **Use \( \pi \approx \frac{22}{7} \)**:
\[ \text{Area} \approx \frac{22}{7} \times 7.84 \]

6. **Calculate \( \frac{22}{7} \times 7.84 \)**:
- First, divide \( 7.84 \) by \( 7 \):
\[ 7.84 \div 7 = 1.12 \]
- Now multiply by \( 22 \):
\[ 22 \times 1.12 = 24.64 \]

7. **Final area for part (i)**:
\[ \text{Area} \approx 24.64 \, \text{m}^2 \]

### Part (ii): Radius = 8.4 m

1. **Identify the radius**:
- The radius \( r = 8.4 \) m.

2. **Substitute the radius into the area formula**:
\[ \text{Area} = \pi (8.4)^2 \]

3. **Calculate \( (8.4)^2 \)**:
\[ (8.4)^2 = 8.4 \times 8.4 = 70.56 \]

4. **Substitute \( (8.4)^2 \) back into the area formula**:
\[ \text{Area} = \pi \times 70.56 \]

5. **Use \( \pi \approx \frac{22}{7} \)**:
\[ \text{Area} \approx \frac{22}{7} \times 70.56 \]

6. **Calculate \( \frac{22}{7} \times 70.56 \)**:
- First, divide \( 70.56 \) by \( 7 \):
\[ 70.56 \div 7 = 10.08 \]
- Now multiply by \( 22 \):
\[ 22 \times 10.08 = 221.76 \]

7. **Final area for part (ii)**:
\[ \text{Area} \approx 221.76 \, \text{m}^2 \]

### Summary of Results:
- Area for radius 2.8 m: **24.64 m²**
- Area for radius 8.4 m: **221.76 m²**