A fool wants to tie a rope around the earth. So he buys a rope of 40,000 KM and ties it around the world. His neighbour, also a fool, wants to do the same only he wants the rope on sticks 1 meter above the ground.

How much more rope does he need?
And how much more rope do you need when you use a tennis ball instead of the earth

6 meters 28 centimeters.
The outline of a circle is 2*PI*r. If you want a rope that is one meter above the ground rnew=r+1. So you need 2*PI*(r+1)-2*PI*r more rope.
So,
x=2*PI*(r+1)-2*PI*r
x=2*PI*r+2*PI-2*PI*r
x=2*PI
x=6.28
It does not matter what the radius of the circle is. You always need 2*pi more rope.