Section 12-2: Permutations and Combinations

1
Section 12-2 Permutations and Combinations

• An arrangement in which order IS important is
  called a Permutation.
• Formula
• n objects taken r ways. (n is always
  greater than or equal to r)
• EXAMPLE How many different ways can I arrange 8
  students in 5 desks?

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• An arrangement in which order is NOT important is
  called a Combination.
• Formula
• EXAMPLE How many combinations of 2 colors can I
  choose to paint my wall if there are 7 to choose
  from?

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• Repeating Objects If there are repeating
  objects, it puts a twist on a normal permutation
  problem.
• EXAMPLE How many ways can I rearrange the
  letters in the word FOOTBALL?

Total letters
L repeats twice
O repeats twice