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Permutations

Permutations

From the course: Test Prep: GRE

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Permutations

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- [Voiceover] Permutations are like when we have a problem that asks us something like "How many ways "can five people sit in five chairs?" Okay so let's say we have a problem like that. Well every single possible way is different. So let's say here are the five chairs. And then there's five people over here. Let's call them A, B, C, D and E. So let's think about how we would do this. Well the easiest way to do a permutation I think, is to just say "What are the "possibilities for chair number one?" Well there's five, right, 'cause there's five people. And then how many possibilities are there for chair number two? Well now there's four possibilities, because one possibility is already placed. How many for chair three? Well now we're down to three, and for chair four there's two, then we're finally left with one possibility to chair one. And then to get the answer, we would multiply. Five times four is 20, times three, 60, times two is 120, times one is still 120. So that's the…

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