Derangements: Everything about them and More! (ESSAY)

Here’s a twist on a classic puzzle:
Twenty men check their hats into a cloak room. But the cloak boy is somewhat disorganized and forgets which hats belong to whom and so, at the end of the evening, decides to hand hats back to the gentlemen at random. Ten of the men are lawyers. What is the probability that no lawyer gets his own hat back?

In this essay we talk about everything you could possibly want to know about derangements and “sub-derangements” ( a new term invented for this puzzle!)



    QUADRATICS, Permutations and Combinations, EXPLODING DOTS, and more!

    Written for educators - and their students too! - this website, slowly growing, takes all the content Tanton has developed in his books, videos, and workshops, and organizes it into short, self-contained, and complete, curriculum units proving that mathematics, at all points of the school curriculum, can be joyous, fresh, innovative, rich, deep-thinking, and devoid of any rote doing! Let's teach generations of students to be self-reliant thinkers, willing to flail and to use their common sense to "nut their way" through challenges, to assess and judge results, and to adjust actions to find success. (Great life skills!)


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