A computer security system requires a unique password for each user.The passwords use only letters of the English alphabet (26 possible letters) and cannot contain any repeats; that is, any given letter can be used only once in a password.If passwords have five letters each, how many passwords are available from which to choose?
A) 65,780
B) 11,881,376
C) 7,893,600
D) 130

Question

Quizplus · Accepted Answer

For the first letter, there are 26 options. Then, for the second letter, there are only 25 options left, since we cannot repeat the first letter. Similarly, for the third letter, there are only 24 options left, and so on. So, the total number of possible passwords is:

26 x 25 x 24 x 23 x 22 = 7,893,600

Thus, the answer is choice C.

A Computer Security System Requires a Unique Password for Each