Which formula is used to calculate the area of a circle?

The area of a circle is calculated using the formula A = πr², where A represents the area and r is the radius of the circle. This formula is derived from the concept that the area of a circle is proportional to the square of its radius, multiplied by the constant π (pi), which is approximately 3.14.

This formula reflects the intrinsic relationship between the radius of the circle and the total space contained within it. The radius is the distance from the center of the circle to any point on its circumference, and when squared, it emphasizes how increasing the radius significantly increases the area.

The other options provided represent different geometric calculations that do not pertain to finding the area of a circle. The formula for circumference (C = 2πr) calculates the perimeter of the circle, while another option incorrectly suggests a linear measure, and the last option references the perimeter of a rectangle. Thus, the formula A = πr² exclusively describes the area of a circle.