Puzzle #14: Elon Musk’s Interview Question
You are standing somewhere on the surface of the Earth. You walk 1 mile south, then 1 mile west, and then 1 mile north, and you end up back at the same point where you started. Where are you? Assume the Earth is a perfect smooth sphere.
The most natural answer to this question is the North Pole. And it’s correct! Walking a mile south from the North Pole, then a mile west, and a mile north again will land you right back at the top of the planet. According to Musk’s biographer, Ashlee Vance, when engineers would get this correct, Musk would respond, “Where else could you be?” That problem is significantly tougher, and solving it is your task for the week.
The South Pole doesn’t work. Traveling south from the South Pole isn’t even a meaningful concept, since moving south is by definition moving toward the South Pole. It helps to remember that we’re on a big sphere. Think of lines of latitude not actually as horizontal lines but as circles traced around the globe that get progressively wider toward the equator and narrower toward the poles.
Find the solution at the bottom of this page.
