Permutation

[Kaunteya1]

Here is question that is from GMATPrep. I need some help. I don't have the answers but I am sure someone can figure it out.

The symbols of a stock market can be made up of a single letter, two letters, or 3 letters of the alphabet. ABC represents a different company from CBA, and AB is different than BA. How many possible total companies can be represented from the 26 letter of the alphabet?

The answer is 18 thousand and something. How would you go about this question using permutations and combinations? I haven't the foggiest idea.

[Kaunteya1]

I guess no one knows.

I think I answered the question anyways.

26 Letters for the single representation
26 x 26 for the double representation and
26 x 26 x 26 for the triple.

Answer = 26 + 26^2 + 26^3

[Leo2008]

Hi

This is Permutation with Repetition....your answer is correct
My calculation is the same

26 + (26*26) + (26*26*26)

I posted a question online.......check that out...its a little tricky question