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

$A = \pi r^2$

Where:

• $A$ is the area,
• $r$ is the radius of the circle,
• $\pi$ is a constant approximately equal to 3.14159.

The radius $r$ is half of the diameter. So, for a diameter of 2.5, the radius is:

$r = \frac{2.5}{2} = 1.25$

Now, substitute $r = 1.25$ into the area formula:

$A = \pi (1.25)^2 = \pi (1.5625)$

$A \approx 3.14159 \times 1.5625 \approx 4.9087 \, \text{square units}$

So, the area of the circle is approximately 4.91 square units.

Would you like more details or have any questions?

Here are 5 related questions:

1. What is the circumference of a circle with the same diameter?
2. How does the area change if the diameter is doubled?
3. Can you find the radius of a circle if the area is known?
4. How is the formula for the area of a circle derived?
5. What is the relationship between the diameter and circumference of a circle?

Tip: Always remember, the radius is half the diameter, which is crucial in many circle-related calculations.