To find the circumference of a circle when you have the radius, you can use the formula:
C = 2πr
In this formula, C represents the circumference, π (pi) is a constant approximately equal to 3.14159, and r is the radius of the circle.
For example, if the radius of the circle is 5 units, you would substitute that value into the formula:
C = 2 × π × 5
Calculating that gives you:
C ≈ 2 × 3.14159 × 5 ≈ 31.42 units
This means that the circumference of the circle is approximately 31.42 units. This method provides a straightforward way to determine the distance around the circle based on its radius.