Question 169011:  If the letters A, B, C, D, E, and F are used in a five-letter code, how many different codes are possible if repetitions are not permitted?
 
a) 625 
b) 720 
c) 7776 
d) 1296
 
 
I am completely confused.  
 Answer by Alan3354(69443)      (Show Source): 
You can  put this solution on YOUR website! If the letters A, B, C, D, E, and F are used in a five-letter code, how many different codes are possible if repetitions are not permitted?  
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For the 1st letter, you can choose one of 6. For the 2nd, one of the remaining 5, then 4, 3, 2.  So the possibilities are 6*5*4*3*2*1, or 6! (6 factorial). 
That's 720. 
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