Math Lesson #9: How many 3-letter combinations?

How many combinations of 3 English letters exist? Any combination is fine, even if it's not a valid Engish word. So, "rkq" and "hhh" are ok...

Well, there are 26 English letters, so there are 26 choices for the 1st letter:

And 26 choices for the 2nd:

And 26 choices for the 3rd:

So, the total number of possibilities is 26 * 26 * 26 = 17,576... pretty cool!