A license plate begins with three letters. If the possible letters are A, B, C, D , how many different permutations of these letters can be made if no letter is used more than once?

Question: A license plate begins with three letters. If the possible letters are A, B, C, D , how many different permutations of these letters can be made if no letter is used more than once?

Solution:
For the first letter, there are 5 possible choices. After that letter is chosen, there are 4 possible choices. Finally, there are 3 possible choices.
4 × 3 × 2
= 24