What is the formula used to calculate the circumference of a circle?

The formula to calculate the circumference of a circle is represented as C = 2πr, where 'C' stands for the circumference, 'r' is the radius of the circle, and 'π' (pi) is a mathematical constant approximately equal to 3.14.

This formula arises from the relationship between the radius and the diameter of the circle. Since the diameter is double the radius (d = 2r), the formula can also be expressed as C = πd, which is another valid form but dependent on knowing the diameter instead of the radius.

The use of the radius in the formula (2πr) provides a direct way to calculate circumference based on the radius measurement, which is often more accessible in various scenarios, especially in problems where the radius is already given.

In contrast, the other options presented are related to circle measurements but serve either different purposes or are incorrect for calculating circumference. For instance, C = πr² is actually the formula for the area of a circle, not its circumference. While C = 3.14d approximates circumference using a fixed value for π, it does not utilize the more precise mathematical representation. C = πd, though correct, is merely a different expression of