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The Brainteaser Elon Musk Asks New SpaceX Engineers

Posted by ryuzaki0 on from the riddle-me-this dept.

Nerval's Lobster writes: The latest biography of Elon Musk, by technology journalist Ashlee Vance, provides an in-depth look into how the entrepreneur and tech titan built Tesla Motors and SpaceX from the ground up. For developers and engineers, getting a job at SpaceX is difficult, with a long interviewing/testing process... and for some candidates, there's a rather unique final step: an interview with Musk himself. During that interview, Musk reportedly likes to ask candidates a particular brainteaser: "You're standing on the surface of the Earth. You walk one mile south, one mile west, and one mile north. You end up exactly where you started. Where are you?" If you can answer that riddle successfully, and pass all of SpaceX's other stringent tests, you may have a shot at launching rockets into orbit.

8 of 496 comments (clear)

  1. North Pole by 605dave · · Score: 4, Informative

    I am guessing the answer is the north pole...

    --
    Be kind, for everyone you meet is fighting a difficult battle. - Plato
    1. Re:North Pole by Penguinisto · · Score: 3, Informative

      The answer is indeed the North Pole, and that brain teaser has been around for what, eons now?

      I think I'd quickly answer it, then ask him one that I made up and tested long before that final interview.

      --
      Quo usque tandem abutere, Nimbus, patientia nostra?
    2. Re:North Pole by softarch · · Score: 5, Informative

      Or another ring of points closer to the south pole such that you go completely around the world twice, and another ring closer such that you go around the world 3 times....

      --
      Apply your own interpretation of the words and grammar in this post.
    3. Re:North Pole by IcyWolfy · · Score: 4, Informative

      That's the asymptote that needs to be addressed separate due to a division by 0.

      The correct answer is an infinite number of points around the south pole, with the exception of the south pole itself, and the north pole.

      Or in words:

      Given C = 1 mile, there is an longitudinal (East-West) circle north around the south pole with a circumference of 1 mile.
      Any point on this line is an answer.
      As does any whole divisor of this (1/3 mile circumference is traversed three times in one mile, but back at the same starting point.)

      So C(1/1) + C(1/2) + C(1/3) + C(1/4) + C(1/n)
      And more generally
      = C(1/n) where n != 0 is a circle around the south pole, and n==0 is the north pole solution, whose division by 0 needs resolution by analysis (which is more obvious)

    4. Re:North Pole by Roger+W+Moore · · Score: 5, Informative

      The north pole and a circle of lat 1 + 1 / (2 * PI) north of the south pole.

      Actually the answer is the north pole and a circles of lat 1 + 1 / (2*pi*n) north of the south pole where n=1,2,3,4... etc. plus there is a slight correction because the surface of the earth is not entirely flat and so the circumference of a line of latitude is actually less than 2*pi*s where s is the arc length from the line to the south pole for the distances involved it would probably be negligible compared to surface defects.

  2. Re:Either of the poles woulc cause this effect by just_common_sense · · Score: 3, Informative

    It doesn't work because you cannot walk East or West from the South pole.

  3. One obvious answer and infinite other answers. by LawnBoy · · Score: 3, Informative

    The obvious answer is the North Pole, but there are others. First, find the circle around the South Pole with a circumference of one mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one half mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one third mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Then, find the circle around the South Pole with a circumference of one quarter mile, and then select all the points on the circle with a radius one mile larger around the South Pole. Continue ad nauseum.

  4. No he doesn't... by Anonymous Coward · · Score: 5, Informative

    I interviewed with SpaceX for a senior-level software position last year, and was offered the job but turned it down on logistical grounds.

    I did indeed have to take the tests mentioned here, and did have to interview with Musk himself as the final step. However, he did not ask me this brain teaser question. In fact, he specifically said he doesn't ask brain teaser questions because they are dumb.

    Nor would he likely ask such a well-known and old brain teaser anyway. This seems like one of those things erroneously attributed to "Bill Gates" over the past 20 years because he is famous and smart, and fits people's preconceptions.