Question 165369: Suppose you are playing a word game with seven distinct letters. How many seven-letter words can there be? Answer by nerdybill(7384) (Show Source):
You can put this solution on YOUR website! When "order" is important we refer to it as a "permutation".
When "order" is NOT important we refer to it as a "combination".
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nPr = (n!)/(n-r)!
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In our case:
n = 7
r = 7
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nPr = (n!)/(n-r)!
7_Pr_7 = (7!)/(7-7)!
7_Pr_7 = (7!)/(0)!
7_Pr_7 = (7!)/1
7_Pr_7 = (7!)
7_Pr_7 = (1*2*3*4*5*7)
7_Pr_7 = 840
