sequential counting principle (SCP) Problem- solving tool

Question

If a “word “ is any arrangement of 3 different letters, how many 3-letter “words” can be formed from the letters B,O,N and K, where each letters is to be used once?

Answer 1

For the first letter in the word, there are 4 choices (B, O, N, K).  Once the first letter is chosen, you have 3 choices for the 2nd letter and then 2 choices for the 3rd letter.  Multiplying these together:

4*3*2 = 12*2 = 24 different words.