What formula should be used to find the circumference of a circle

Formula: C = 2πr

For example: The circumference of a circle with a radius of 10 is 62.83

The circumference = π x the diameter of the circle (Pi multiplied by the diameter of the circle). Simply divide the circumference by π and you will have the length of the diameter. The diameter is just the radius times two, so divide the diameter by two and you will have the radius of the circle