The global ocean covers about 70% of the Earth’s surface. If all the ocean water was uniformly distributed over the whole surface, what would be its depth? Assume that the Earth is a perfect sphere, and the average ocean depth is 4 km.

Answer 1

volume of water:
area*depth=.7*4PIre^2*4000

so if it is spread..
area*depth=4PIre^2*depth

because it is the same volume of water,
.7*4PI*re^2*4000=4PI*re^2*d

d=4000*.7 m