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

$\text{Area} = \pi r^2$

Where $r$ is the radius of the circle. The radius is half the diameter, so for a circle with a diameter of 5, the radius $r$ is:

$r = \frac{5}{2} = 2.5$

Now, we substitute $r = 2.5$ into the area formula:

$\text{Area} = \pi (2.5)^2 = \pi \times 6.25$

Approximating $\pi$ as 3.14:

$\text{Area} \approx 3.14 \times 6.25 = 19.625$

So, the area of the circle is approximately 19.625 square units.

Would you like more details or have any questions?

Here are some related questions you can explore:

1. What happens to the area of a circle if the radius is doubled?
2. How do you find the circumference of a circle if you know the diameter?
3. What is the relationship between the diameter and the radius of a circle?
4. How does changing the value of $\pi$ affect the area of a circle?
5. Can the formula for the area of a circle be used for ellipses?

Tip: When dealing with circles, it's often easier to work with the radius since the formulas for both area and circumference are based on the radius.