Hats and Derangements (VIDEO!)

A lazy teacher hands 20 graded assignments back to his 20 students – randomly. What is the probability no student receives her own paper? A hat check clerk forgets who handed in which hat and so decides to return them at random. What are the chanced no-one receives his own hat?

In this video we find a formula for the number of derangements of N objects and show the classic appearance for the number e.

Derangements

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  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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• Books

  • Thinking Mathematics! (TEN VOLUMES)
  • Solve This: Mathematical Activities for Students and Clubs
  • Encyclopedia of Mathematics
  • Geometry I & II

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  Email: tanton.math@gmail.com