TITLE: How do we deal with questions that don't state whether repetition is allowed or not?
QUESTION [0 upvotes]: Just like the question, in most books there are questions that don't state whether repetition is allowed or not. How do we deal with it? Do I need to compute it as if repetition is allowed then as if repetition is not allowed?
Example:
Using the vowels of the English alphabet, how many different possible 3-letter code words can be formed?

REPLY [1 votes]: Look at the plain meaning of the words in the question, and think about examples.
Would a string of characters with repetition make sense as a "code word", in the common sense of the phrase?  Would AAA be something you would call a code word?  How about BOB?
It seems clear to me that the answer is yes, so repetition is allowed here.
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