Question

How many miles to earth's core?

Answer 1

That's really the mean radius of the Earth, which is about `"6371 km"`. You may have used that number in physics.

To convert it to miles:

`6371 cancel"km" xx (10^5 cancel"cm")/(1 cancel"km") xx (1 cancel"in.")/(2.54 cancel"cm") xx (1 cancel"ft.")/(12 cancel"in.") xx "1 mi."/(5280 cancel"ft.")`

`~~ color(blue)" 3958.76 mi"`