Assume radius of earth = r feet
If the man walks around the circumference of the earth, is feet would travel:
(2 x pi x r) feet
Assume height of man = h feet
His head is r + h feet from the centre of the earth, so on the same journey, his head would travel:(2 x pi x (r + h)) feet = (2 x pi x r) + (2 x pi x h)
The difference in distance that the feet and gead have travelled:
= (2 x pi x r) + (2 x pi x h) - (2 x pi x r) = 2 x pi x h
Assume pi = 3.14 and man's height = 6 feet:
Head travels an extra (2 x 3.14 x 6 ) feet = near enough 36 feet (depending on what height you assume for the man)