Answer:
diameter
circumference

diameter
Step-by-step explanation:
First, find the length of the diameter (d) and the length of the circumference of the circle (c).
Next, divide the length of the circumference c by the length of the diameter d and set up an equation

where the ratio equals to
(the definition of
)
Then, solve the equation for the circumference c:

Finally, substitute 2 times the radius for the diameter
