Combinations and Permutations

nickar1172

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Dec 11, 2013
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Reviewing for finals and got this question wrong:

How many different permutations are there of the letters in the word LOLLIPOP

what I did was 8P8, how would you solve this?
 
Reviewing for finals and got this question wrong:

How many different permutations are there of the letters in the word LOLLIPOP

what I did was 8P8, how would you solve this?

You have to account for the fact that you have multiples of the same letters. So doing 8! as you did means that you are counting each of the L's, O's and P's as different letters, which they are not. You need to divide 8! by the product of the factorials of the number of repeating letters for each repeating letter. In this case there are 3 L's, 2 O's and 2 P's. Thus, the number of permutations would be:

\(\displaystyle \dfrac{8!}{3! \cdot 2! \cdot 2!}\)
 
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