How Would You Move Mount Fuji?

If you like solving brain teasers, try out the puzzles in William Poundstone's How Would You Move Mount Fuji? : Microsoft's Cult of the Puzzle -- How the World's Smartest Companies Select the Most Creative Thinkers. Poundstone visited Microsoft and other high tech companies to harvest the best puzzles that interviewers ask job applicants. (or used to ask -- I understand Microsoft doesn't routinely ask these kinds of questions any longer).

Excerpt:

"With the 1990s dot-com boom and bull market in full swing, Microsoft was famous as a place where employees of no particular distinction could make $1 million before their thirtieth birthday. Grad student Gene McKenna signed up for an interview with Microsoft's recruiter.

Suppose you had eight billiard balls, the recruiter began. One of them is slightly heavier, but the only way to tell is by putting it on a scale against the others. What's the fewest number of times you'd have to use the scale to find the heavier ball?

McKenna began reasoning aloud. Everything he said was sensible, but somehow nothing seemed to impress the recruiter. With hinting and prodding, McKenna came up with a billiard-ball-weighing scheme that was marginally acceptable to the Microsoft guy. The answer was two.

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