A password consists of 3 randomly selected letters, which must be in the correct order. There are 26 letters in the alphabet. How many passwords are possible if no letter may be repeated?
26*25*24=15600
or
$$^{26}P_3 =$$ $${\left({\frac{{\mathtt{26}}{!}}{({\mathtt{26}}{\mathtt{\,-\,}}{\mathtt{3}}){!}}}\right)} = {\mathtt{15\,600}}$$
what are you a hacker?
we can make 24 passwords
