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Puzzle Details

At the equator the radius of the earth is 6,378 km, so its circumference is almost exactly 40,000 km.

Imagine we had a long rope which went around the equator, this would of course be 40,000 km long.

If we now placed 1 metre sticks vertically all the way around and lay the rope on top of these sticks (i.e. the rope would be 1m higher all the way around) how much extra rope would we require?

[Ref: ZFOV]

Answer: 6.28 metres, a lot less than you might think!

If we call the radius of the Earth (in metres), R. Then the difference between the two circumferences is:

2*Pi*(R+1) - 2*Pi*R = 2*Pi metres = 6.28 metres. QED.

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