Question

What happens to the circumference of a circle when the radius is quadrupled?

Answer 1

He circumference of a circle is equal to the diameter times pi. So, let's look at what happens if you double the radius of a circle -- say from 2 to 4. The area will go from 12.56 to 50.24. This means that it has quadrupled.

Answer 2

Circumference = 2 * PI * radius
The circumference would also be quadrupled.
There is a direct relationship between circumference and radius.