Question

Which of the following correctly relates the measures of the diameter (d) and radius (r) of a circle?

A) d= r/2
B) r=2d
C) r= d/2
D) d= 2/r

Answer 1

It all depends on what your looking for.
Area= 3.15*r* squared(2)

Answer 2

C) r= d/2
that's the answer