circumference is actually a closed boundary of a curved geometric figure like circle.
it can be calculated by applying the formula C = π * d ( d= diameter)
or C = 2πr ( r= radius)
you can use any one to find out the circumference of the circle.
But from your attached document,it is clear that circumference is given, sorry, I don't understand for what you are looking for?
diameter goes straight through the center of a circle and touches the boundaries of the circle in both sides.
Diameter is always double of radius, D = 2r ( r= radius)
or you can find radius by dividing it by 2,
r = D/2
I hope it will serve your purpose.
