Lesson Permutations

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This Lesson (Permutations ) was created by by Shin123(626) About Me : View Source, Show
About Shin123: Just a kid who solves math problems for fun :)
This lesson will teach you about permutations. The 2 ways to write permutations are P(n,r) and nPr. The formula is
nPr=n%21%2F%28n-r%29%21

Problem 1


How many ways are there for 10 people to finish in top 3?

Solution 1

There are P(10,3) ways for the 10 people to finish in top 3.
10%21%2F%2810-3%29%21
10%21%2F7%21 There are 720 ways. We used permutations because order matters. Combinations are used when order does not matter.

Problem 2


How many ways are there to arrange the words in the word COUNTING?

Solution 2

There are 8P8 ways.
8%21%2F%288-8%29%21
8%21%2F0%21 There are 40320 ways but we must divide by 2! because there are 2 Ns. So there are 20160 ways.
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