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Puzzle 1.Suppose I have a box of jewels. The average value of a jewel in the box is \$10. I randomly pull one out of the box. What’s the probability that its value is at least \$100?•

Puzzle 2.Suppose I have a box full of numbers—they can be arbitrary real numbers. Their average is zero, and their standard deviation is 10. I randomly pull one out. What’s the probability that it’s at least 100?

John Baez and Brendan Fong claim to have answered questions like these, but in a general way that is useful for quantum mechanics: