The slant height of Mount Fuji, assuming it to be a geometric cone, is 22.82 km. The volcano has an average base radius r = 22.5 km and we can approximate its height to h = 3.8 km. To climb up Mount Fuji on a straight line, you have to walk:
l = sqrt(r² + h²) = sqrt(22.5² +3.8²) = 22.82 km
Surprisingly, this is pretty close to the length of the actual trail!
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