What is the circumference of a circle calculated as?

The circumference of a circle is calculated using the formula C = 2πr, where 'C' represents the circumference and 'r' represents the radius of the circle. This formula derives from the relationship between the diameter and the radius, as the circumference is the total distance around the circle. The factor of 2π comes from the fact that the circumference is equal to the diameter (which is 2r) multiplied by π.

The other options represent different mathematical concepts. The formula A = πr² calculates the area of a circle, measuring the space contained within it. The formula B = 4/3πr³ is used for the volume of a sphere, representing three-dimensional space. Lastly, the formula D = πr²h is for the volume of a cylinder, which takes both the circular area and height into account. Each of these formulas is significant in its own context but is not applicable to the calculation of the circumference of a circle.