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Gprep - permutation n combination

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26^4(27)

by ektamatta » Mon Jun 30, 2008 3:32 pm
If it is a 4 letter code:

26 x 26 x 26 x 26 (Since the letters don’t have to be distinct. You are selecting from the same pool of 26 each time).

Similarly, for a 5 letter code:

26 x 26 x 26 x 26 x 26

=> Total = 26^5 + 26^4
= 26^4 (26 + 1) 26^4 is common
= 26^4(27)
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