Question

How do I do this problem?

Answer 1

The formula for the circumference of a circle:
C = 2(π)(r)

To solve for r, just divide both sides by 2π.
C/2π = r

For this problem, you are given the C, so plug that into the equation.
8π = 2(π)(r)

Now to solve for r, just divide both sides by 2π
4 = r

The radius of the circle is 4.