SOLUTION: Carl is choosing a four-character password for his cell phone. The password can contain letters and digits only, and can't include repeating characters. How many passwords are

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Question 1139436: Carl is choosing a four-character password for his cell phone. The password can contain letters
and digits only, and can't include repeating
characters. How many passwords are possible?

Answer by ikleyn(52777) About Me  (Show Source):
You can put this solution on YOUR website!
.

In all, Carl can use 26 + 10 = 36 symbols.


Without repeating, there are  36*35*34*33 = 1413720 different possible codes.



Any of 36 symbols in the very first leftmost position;

then any of 35 remaining symbols in the 2-nd position;


    . . .  and  so  on  . . .