The circumference of a circle can be calculated using the formula:
C = 2πr
where C is the circumference and r is the radius.
In this case, we know that the circumference (C) is 36π cm. We can set up the equation:
36π = 2πr
Next, we can divide both sides of the equation by 2π to solve for r:
r = 36π / 2π
Now, simplifying the right side:
r = 36 / 2
r = 18
Therefore, the length of the radius r is 18 cm.