With at least one letter repeated, how many different eight-letter words can be created using the letters A through J?
From A to J, there are 10 letters.
The total number of 8-letter words that can be formed using 10 different letters (with or without repetition). Because each position in the 8-letter word can be filled in 8 different ways.
So, the required number is
The number of 8-letter words that can be formed with 10 different digits, with no digit repeated.
So, the number is
The difference between these two numbers is the answer. Now, from the set of all the words, remove those that have no letter repetition, and you have the set.
Therefore, the different 8-letter words can be formed in ways
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