Counting A computer hacker is trying to break into a computer system by guessing
ID: 3047216 • Letter: C
Question
Counting A computer hacker is trying to break into a computer system by guessing the system administrator's password. The hacker can try 15 passwords a minute, but if he tries unsuccessfully for more than 12 minutes a day, he will get caught. If he limits his attempts to at most 12 minutes each day, he will not get caught. The hacker knows that the administrator's password is at least 6 and at most 10 characters long, does not contain any character that is not a number, an uppercase letter, or a lowercase letter (no special characters such as spaces, punctuation marks, dollar signs, etc.), and that the first character is a letter. Case matters, and characters can be repeated. Problem 9 How many passwords are there that start with a letter, contain only numbers and upper and lowercase letters, and are exactly 10 characters long? (Q9)Explanation / Answer
Password starts with a letter So there are 26 lower and 26 uppercase cases=> total 52 cases
And for remaining 9 places there are total 62 cases(52 letters and 10 integers)
Total passwords = 52 * (62)9 = 7.039285*1017