ACT Math : How to find permutation notation
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Example Questions
Example Question #1 : How To Find Permutation Notation
In permutation notation, what does 8P4 represent?
336
1680
6720
210
1680
The expression 8P4 represents the number of permutations of 8 objects arranged 4 at a time. Thus, 8 x 7 x 6 x 5 = 1680
Example Question #11 : Permutation / Combination
How many different ways can five books be lined up on a shelf?
80
150
100
60
120
120
Order matters, so we use permutations: (5)(4)(3)(2)(1) = 120
There are five possibilities for the first book, four possibilities for the second book, three for the third, and two for the fourth, and one possibility for the last book.
Example Question #1721 : Act Math
How many different ways can cheese slices be stacked in piles containing 
Since the order matters, you are dealing with a permutation in this question. A permutation like this could be done with the equation:
For our values, this would be:
However, it is easiest just to think of this like it has 
more easily.
This is 
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