7. Calculating Permutations

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Permutations tell us how many ways we can arrange a set of objects, and are used in many probability problems. Learn how to calculate the number of permutations a problem has in this lesson.


  1. Lesson Goal (00:14)

    The goal of this lesson is to learn what permutations are and learn how to calculate them.

  2. Overview of Permutations (00:44)

    A permutation is an ordered arrangement of some or all of the items in a set. For example, if we have a series of 5 colored squares, any ordered arrangement of these squares represents a different permutation. 

    We may want to find the number of possible permutations for a set of items. To do this, we can consider the process of creating a new permutation. As an example, if we have 5 items, there are 5 possible items we can put in the first slot, 4 possible items for the second slot, and so on. As a result, the number of permutations is 5 x 4 x 3 x 2 x 1, which is 120.