new secretary has been given n computer passwords, only one of which will permit access to a computer file. Because the secretary has no idea which password is correct, he chooses one of the passwords at random and tries it. If the password is incorrect, he discards it and randomly selects another password from among those remaining, proceeding in this manner until he finds the correct password. (a) What is the probability that he obtains the correct password on the first try? (b) What is the probability that he obtains the correct password on the second try? What is the probability that he obtains the correct password on the third try? (c) A security system has been set up so that if four incorrect passwords are tried before the correct one, the computer file is locked and access to it is denied. If n = 7, what is the probability that the secretary will gain access to the file
new secretary has been given n computer passwords, only one of which will permit access to a computer file. Because the secretary has no idea which password is correct, he chooses one of the passwords at random and tries it. If the password is incorrect, he discards it and randomly selects another password from among those remaining, proceeding in this manner until he finds the correct password. (a) What is the probability that he obtains the correct password on the first try? (b) What is the probability that he obtains the correct password on the second try? What is the probability that he obtains the correct password on the third try? (c) A security system has been set up so that if four incorrect passwords are tried before the correct one, the computer file is locked and access to it is denied. If n = 7, what is the probability that the secretary will gain access to the file
A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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A new secretary has been given n computer passwords, only one of which will permit access to a computer file. Because the secretary has no idea which password is correct, he chooses one of the passwords at random and tries it. If the password is incorrect, he discards it and randomly selects another password from among those remaining, proceeding in this manner until he finds the correct password.
(a)
What is the probability that he obtains the correct password on the first try?
(b)
What is the probability that he obtains the correct password on the second try?
What is the probability that he obtains the correct password on the third try?
(c)
A security system has been set up so that if four incorrect passwords are tried before the correct one, the computer file is locked and access to it is denied. If
n = 7,
what is the probability that the secretary will gain access to the file? (Enter your probability as a fraction.)Expert Solution
Step 1
Given,
The new secretary has n computer passwords,
out of which only 1 is correct.
Now, a password is selected from n given passwords without replacements.
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