How many 4-character passwords can you make from the letters A, B, C, D, and E if you allow no repetition? In other words, you can have ABCD, but not AABC or ABCA.

Answer 1

n = 5 letters (A, B, C, D, and E)

The password will have 4 characters, which means we only have 1 letter per character without repeats.

You have 5 possible letters to choose from for the first slot. Then you have 4 possible letters to choose from for the second slot. You keep going until all the slots are full.

5*4*3*2 = 120 possible passwords