Calculate combinations of characters My first post here...not really a math expert, but certainly enjoy the challenge.
I working writing a random string generator and would like to know how to calculate how many possible combinations there are for a particular combination.
I am generating a string of 2numbers followed by 2 letters (lowercase) e.g. 12ab
I think the calculation would be (breaking it down) 
number combinations 10*10=100
letter combinations 26*26=676
So the number of possible combinations is 100*676=67600, but this seems a lot to me so I'm thinking I am off on my calculations!!
Could someone please point me in the right direction?
Thx

You are right. That is the most basic/fundamental procedure for counting in combinatorics.
It's sometimes called the Rule of product, or multiplication principle or fundamental counting principle, and it can be visualized as a tree
