Sunday, January 29, 2012

Permutations and Combinations

This weekend I am going to teach you all how to work problems that involve permutations and combinations. These are probability problems. Before I show you an example, there are a few things that you need to know about permutations and combinations.

Notes:
• You use permutation when the order is important
• You use combination when the order is not important
• nPr = (n!)/(n-r)! is the formula for permutation
• nCr = (n!)/(n-r)!r! is the formula for combination
• n will always be the larger number in a permutation or combination problem
• These problems can also be solved by inputting the information into your calculator

Example: In how many ways can a organization with 15 members choose 5 different officers?
• All of the officers are different, so that means that the order is important. You would use permutation for this problem.
• So n=15 and r=5, 15P5
• Your final answer would be 360,360

-Braxton

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