SOLUTION: To keep computer files secure, many programs require the user to enter a password. The shortest allowable passwords are typically six characters long and can contain both numbers a

Question 445787: To keep computer files secure, many programs require the user to enter a password. The shortest allowable passwords are typically six characters long and can contain both numbers and letters. How many six-character passwords are possible if (a) characters can be repeated and (b) characters cannot be repeated?
on (a) this is what i tried... 26^6 x 26^5 x 10 x 26^4 x 10^2 etc. but the number I get is way off from the back of the book I also tried 36P6 but that was also incorrect. I have no idea how to continue input would be much appreciated :)

Answer by sudhanshu_kmr(1152) (Show Source): You can put this solution on YOUR website!

any position can be fill by 36 ( 26+10) characters.
(a) no. of possible password = 36*36*36*36*36*36 = 2176782336

(b) no. of possible password when repetition not allowed = 36P6 = 1402410240

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