A possible permutations/combination problem

• Apr 15th 2013, 06:12 PM
chopper07
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
• Apr 15th 2013, 06:49 PM
chiro
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?
• Apr 15th 2013, 06:52 PM
chopper07
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?
• Apr 15th 2013, 06:55 PM
chiro
Re: A possible permutations/combination problem
Independence means that if you change one thing, it doesn't affect the others in any way.
• Apr 15th 2013, 06:56 PM
chopper07
Re: A possible permutations/combination problem
yes each character is independent
• Apr 15th 2013, 08:41 PM
chiro
Re: A possible permutations/combination problem
So multiply the choices of each character to get the total number for all characters.