### Brain Teasers

# Tennis Balls & Planets

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?

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?

### Answer

6 meters 28 centimeters.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 meters more of rope for each additional meter of radius added.

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