To find the area of a circle, you can use the formula:
\[ \text{Area} = \pi r^2 \]
where \( r \) is the radius of the circle.
Given that the diameter is 10 millimeters, the radius \( r \) is half of the diameter:
\[ r = \frac{10 \text{ mm}}{2} = 5 \text{ mm} \]
Now, using \( \pi \approx 3.14 \):
\[ \text{Area} = 3.14 \times (5 \text{ mm})^2 \]
Calculating \( (5 \text{ mm})^2 \):
\[ (5 \text{ mm})^2 = 25 \text{ mm}^2 \]
Now plug this into the area formula:
\[ \text{Area} = 3.14 \times 25 \text{ mm}^2 = 78.5 \text{ mm}^2 \]
Therefore, the area of the circle is 78.5 square mm.