At a certain company, passwords must be from 4-6 symbols long and composed from the 26 uppercase letters of the Roman alphabet, the ten digits 0-9, and the 14 symbols !, @, #, $, %, ^, &, *, (, ), -, +, {, and ). Use the methods illustrated in Example 9.3.2 and Example 9.3.3 to answer the following questions. (a) How many passwords are possible if repetition of symbols is allowed? If repetition is allowed, there are 50 v choices for each entry in the password. So, by the multiplication rule : , the number of passwords of length n is 50 x . Because passwords may have length 4, 5, or 6, by the addition rule 9v , the total number of passwords consisting of 4, 5, or 6 symbols is 15943750000 (b) How many passwords contain no repeated symbols? (Hint: In this case, each additional symbol is entered.) symbols are entered into a password one by one, the number of choices for each entry decreases by 1 as The total number of passwords consisting of 4, 5, or 6 symbols, each of which has no repeated symbol, is 11701082400 (c) How many passwords have at least one repeated symbol? . Thus, the number of passwords with a The number of passwords with at least one repeated symbol plus the number of passwords with no repeated symbols is 15943750000 least one repeated symbol is 4242667600 (d) What is the probability that a password chosen at random has at least one repeated symbol? (Round your answer to the nearest tenth of a percent.) 26.6 %
At a certain company, passwords must be from 4-6 symbols long and composed from the 26 uppercase letters of the Roman alphabet, the ten digits 0-9, and the 14 symbols !, @, #, $, %, ^, &, *, (, ), -, +, {, and ). Use the methods illustrated in Example 9.3.2 and Example 9.3.3 to answer the following questions. (a) How many passwords are possible if repetition of symbols is allowed? If repetition is allowed, there are 50 v choices for each entry in the password. So, by the multiplication rule : , the number of passwords of length n is 50 x . Because passwords may have length 4, 5, or 6, by the addition rule 9v , the total number of passwords consisting of 4, 5, or 6 symbols is 15943750000 (b) How many passwords contain no repeated symbols? (Hint: In this case, each additional symbol is entered.) symbols are entered into a password one by one, the number of choices for each entry decreases by 1 as The total number of passwords consisting of 4, 5, or 6 symbols, each of which has no repeated symbol, is 11701082400 (c) How many passwords have at least one repeated symbol? . Thus, the number of passwords with a The number of passwords with at least one repeated symbol plus the number of passwords with no repeated symbols is 15943750000 least one repeated symbol is 4242667600 (d) What is the probability that a password chosen at random has at least one repeated symbol? (Round your answer to the nearest tenth of a percent.) 26.6 %
Algebra and Trigonometry (MindTap Course List)
4th Edition
ISBN:9781305071742
Author:James Stewart, Lothar Redlin, Saleem Watson
Publisher:James Stewart, Lothar Redlin, Saleem Watson
Chapter14: Counting And Probability
Section14.CT: Chapter Test
Problem 3CT: An Internet service provider requires its customer to select a password consisting of four letters...
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