Answer:
multiply the radius by 2π
Explanation:
The formulas for circumference of a circle is
C = πD where D is the diameter,
or
C = 2πr where r is the radius.
Either formula is correct, but we will work with the second one since the question is asking about radius.
We see that 2π(r) = the circumference, so multiply r by 2π to get the circumference