1. ## Radio Station Call Letters

How can I solve this problem without using the fundamental counting principle?

How many different 4-letter radio station call letters can be arranged if the first letter must be W or K and the letters may be repeated?

I was told this is a permutation NOT a combination word problem.

In that case, can I apply nPn or nPr. If not, why not?

2. Originally Posted by sharkman
How can I solve this problem without using the fundamental counting principle?

How many different 4-letter radio station call letters can be arranged if the first letter must be W or K and the letters may be repeated?

I was told this is a permutation NOT a combination word problem.

In that case, can I apply nPn or nPr. If not, why not?
As far as I know, any formula you could use would be based on the fundamental counting principle. The problem is short enough that you could use a tree diagram to solve it, so maybe that's what they want from you.

3. ## then....

Originally Posted by garymarkhov
As far as I know, any formula you could use would be based on the fundamental counting principle. The problem is short enough that you could use a tree diagram to solve it, so maybe that's what they want from you.
If it's that easy, can you show me how to use the tree method to solve this question?

4. Originally Posted by sharkman
If it's that easy, can you show me how to use the tree method to solve this question?
Sorry, sharkman, I misread the first time I replied. If all 26 letters of the alphabet are at your disposal (except for the first letter), a tree diagram would be too time consuming and enormous to draw. Unless there is some other information you haven't given, I don't know of a way to solve this without using the fundamental counting principle or one of the formulas that is based on that principle.

Maybe someone else can help...