Question

What is the relation between the radius of circle and the area of circle?

Answer 1

Radius is from the center of the circle to the circle's edge.
The DIAMETER is edge to edge with the line going through the radius. 

Answer 2

given area of circle= to the formula of area ofcircle
get the area by further solving..
given area =
$given \: area \: = 4\pi \: r ^{2}$