Answer:
Since the order of choice matters, we will permute the values. a bit more explanation for this:
If the order of choice did NOT matter, ABC and BCA will be counted as one since order of choice does NOT matter
Since order of choice does matter, ABC , BCA and CAB are all different possibilities for the arrangement of the same 3 letters
Since we have 3 slots:
___ ___ ___
Now, for the first slot. You can out either one if the 4 alphabets in the first slot since no slot has been used as of now
So:
_4_ ___ ___
**Keep in mind that the 4 is the possible number of values this slot can have**
Now that one slot has been used, one of the 4 alphabets has been used and since we are not allowed to repeat the same alphabets, we are left with 3 more alphabets
we can put any one of the 3 alphabets in this second slot, Hence:
_4_ _3_ ___
Now that 2 of the 4 alphabets have been used, we are left with only 2 alphabets, so there are only 2 possible alphabets for slot 3
Therefore:
_4_ _3_ _2_
Now that we know the possible alphabets for all 3 slots, we will multiply them with each other to get the total possible number of 3 - alphabet words we can make with 4 alphabets
Total possible words = 4 * 3 * 2
Total possible words = 24
We could've used the formula for Permutation as well