You might think you're clever but could you survive this brainteaser Elon Musk uses to screen potential employees?

During SpaceX's early years, the CEO personally interviewed nearly all of its first one thousand workers — a group that included janitors and technicians, according to an authorized biography by Ashlee Vance.

He continued to interview the company's engineers as SpaceX grew, says Vance. Those who have made it to this hiring stage have likely answered Musk's favorite riddle:

"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?"

While there are many ways to approach this brain teaser, there are two common responses. The first, which most engineers guess correctly, is the North Pole. If you start at the North Pole and go one mile south, then one mile west and finally one mile north, you'll make a triangular path and end up back at the North Pole, your point of origin.

Once the applicant arrives at this answer, Musk then asks, "Where else could it be?" A second answer to the puzzle is near the South Pole, where the Earth has a one mile circumference. You'll walk one mile south to reach this circle, trace that mile-long circle's path, and return one mile north to your starting point. Fewer engineers give this answer, according to Vance.

To gauge responses to Musk's riddle, CNBC Make It took the question to the streets of Manhattan, posing it to people of all ages and backgrounds, including accountants, nurses, students, actors and bartenders. Just one person gave a correct answer.

Luckily for his applicants, Musk doesn't place much emphasis on whether applicants give the right answer, explains the author. Instead, he uses their response to analyze how they process information and approach problem solving.

Given SpaceX's mission, to send humans to Mars, employees must be able to reason their way through problems and find novel solutions.

Musk has discussed recruiting problem solvers before. Speaking at the World Government Summit in Dubai last year, the tech billionaire revealed that when interviewing candidates he also asks them: "What were the most difficult problems you faced and how did you solve them?"

From this question, Musk says he can tell whether the applicant took ownership of a project's problems and solutions or whether the candidate was merely a member of a larger team that did so.

"People [who] really solved the problem, they know exactly how they solved it," Musk explained. "They know the little details."

—Video by Beatriz Bajuelos Castillo

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