with no repeats, there are 26P5 = 7893600 passwords
with repeats, there are 26^5 = 11881376 passwords
So, the probability of no repeats is 26P5/26^5 = 0.6643
I really need help on this problem, if anyone could help id be very grateful.
A password with 55 characters is randomly selected from the 2626 letters of the alphabet. What is the probability that the password does not have repeated letters, expressed to the nearest tenth of a percent?
2 answers
I am going to assume 16 letters, three letter password
pick a letter
there are 15 left
what is the probability of getting a different one next?
15/16
there are 14 left
what is the probability of getting one of them?
14/16
so far we have 16/16 * 15/16 * 14/16
looks like (number of letters! - number not used in password!)/ number of letters
pick a letter
there are 15 left
what is the probability of getting a different one next?
15/16
there are 14 left
what is the probability of getting one of them?
14/16
so far we have 16/16 * 15/16 * 14/16
looks like (number of letters! - number not used in password!)/ number of letters
1 answer