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Example 1
In how many ways can 5 people sit on a 5 person bench?
In this case, we cannot have repeating values. If someone named Bob is already sitting, he cannot appear again at a different place on the bench!
1. Figure out how many places there are to fill
There are 5 seats on the bench, so there are 5 places:
__ __ __ __ __
2. Figure out how many objects potentially can go into each place
There are 5 people who could sit in the first seat. Once someone actually does sit, though, there are only 4 people who could sit in the second seat. For the third seat, there are only 3 people left, and then 2 and then 1. So the places will look like this:
_5_ _4_ _3_ _2_ _1_
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