### Derangements and Hats (TANTON Mathematics)

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.

Length:
09:25