Using the letters A and B, the following two-letter code words can be formed: AA, AB, BB, BA. Using the letters A, B, and C and D, how many different four-letter code words can be formed?
Using the letters A, B, and C and D, how many different four-letter code words can be formed?
This would be the permutation of 4 things taken 4 at a time, abbreviated 4P4 in math.
There are 4 choices for the 1st letter,
There are 3 choices for the 2nd letter,
There are 2 choices for the 3rd letter,
There remains 1 choice for the 4th. The total number is 24.
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