# Thread: A possible permutations/combination problem

1. ## A possible permutations/combination problem

Suppose that your computer password must contain four characters, must begin with a letter, and may contain digits and letters only. How many different passwords can you create?

I've been learning permutations and combinations at the same time, does this count as a permutation problem? I don't think it does, and I'm not sure how to approach this

2. ## Re: A possible permutations/combination problem

Hey chopper07.

You are better off thinking of it using first principles and not as a "A or B type problem".

When things are independent, you multiply.

How many combinations di you have for each character? Is each character independent from all the others?

3. ## Re: A possible permutations/combination problem

what do you mean when you ask if each character is independent?

so do I multiply 26 x number of digits/letters?

4. ## Re: A possible permutations/combination problem

Independence means that if you change one thing, it doesn't affect the others in any way.

5. ## Re: A possible permutations/combination problem

yes each character is independent

6. ## Re: A possible permutations/combination problem

So multiply the choices of each character to get the total number for all characters.