Question

How many different 4-letter codes obtained using the letters A,B,C,D and E without repetitions?
@skullpatrol just to double-check my answer

Answer 1

From 5 letters you have to pick any 4 where order does matter.
5P4 = 5!/(5-4)! = 5!/1! = 5!

or = 5 x 4 x 3 x 2 = 120

another way is to fix one letter at a time.
If A is fixed we must arrange the 4 others = 4! ways
If B is fixed, same thing we get 4! ways
Doing this for each of the 5 letters gives 5 x 4! = 5! ways

Answer 2

yay! got the same answer here..
Thank you @mww ^