What is the formula for the circumference of a circle?

The formula for the circumference of a circle is given by C = 2πr. This formula captures the relationship between the radius (r) of a circle and its circumference (C). The constant π (pi) is approximately 3.14 and represents the ratio of the circumference of any circle to its diameter.

When using this formula, you can easily find the circumference by simply doubling the radius and then multiplying by π. This reflects the fact that the total distance around the circle is proportional to its radius.

Furthermore, the formula C = πd, where d represents the diameter, is also a valid expression for circumference. Since the diameter is twice the radius (d = 2r), this formula can be derived from C = 2πr.

The choice that involves adding lengths (2l + 2w) pertains to the perimeter of a rectangle rather than a circle, further highlighting the specificity of the circumference formula to circular shapes. Thus, the second option accurately captures the mathematical relationship needed to determine the circumference of a circle.