NMH
Banned
OK, think this is the real answer
Answer should be slightly less than 20, all units the same. Assuming the Earth is spherical it's this
2*(12756.32/2)*Sin(((20*1.609344)/(12756.32*pi)*360)/2)
=19.9999918 km
but cos the diameter is smaller North to South it's a bit less but i can't do that
It would be funny to submit that answer, might have the judges scratching their heads a bit.