hey im having trouble getting started on this question:
how many strings of at least one and at most three characters from the alphabet have their characters in alphabetical order? repeated characters are allowed and strings such as aab are in alphabetical order.
i figured with only one character strings, the number of alphabetically-ordered strings is 26, because each string will only have 1 letter, thus n alphabetical order.
im getting stuck with 2 and 3 characters in the string. i considered starting with each letter in the string, but that was going to take too long. i know it has something to do with commutations/pemutations...
with 2 character strings, i guess u could do sum of (26-r) from r=0 to 25...cause for the first letter r=0 (ie. a) there are 26 ways, r=1 (b), there are 25 ways etc...but this doesnt have anything to do with commutations/permutations??