To find the area of a circle using the diameter, you can use the following formula:
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The area \( A \) of a circle is given by: \[ A = \pi r^2 \]
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Since you have the diameter, you first need to find the radius \( r \). The radius is half of the diameter: \[ r = \frac{d}{2} = \frac{21 \text{ mi}}{2} = 10.5 \text{ mi} \]
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Now, substitute the radius into the area formula: \[ A = \pi (10.5)^2 \] Using \( \pi \approx 3.14 \): \[ A = 3.14 \times (10.5)^2 \] First, calculate \( (10.5)^2 \): \[ (10.5)^2 = 110.25 \] Now, substitute that back into the area equation: \[ A = 3.14 \times 110.25 \]
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Perform the multiplication: \[ A \approx 346.19 \text{ mi}^2 \]
So, the area of the circle is approximately 346.19 mi².
The correct response is: 346.19 mi²