BackIn Exercises 49-53, use counting principles to find the probability.
53. A corporation has six male senior executives and four female senior executives. Four senior executives are chosen at random to attend a technology seminar. What is the
probability of choosing
c. two men and two women?
In Exercises 49-53, use counting principles to find the probability.
51. A shipment of 200 calculators contains 3 defective units. What is the probability that a sample of three calculators will have
c. at least one defective calculator?
In Exercises 49-53, use counting principles to find the probability.
53. A corporation has six male senior executives and four female senior executives. Four senior executives are chosen at random to attend a technology seminar. What is the
probability of choosing
b. four women?
You work in the security department of a bank’s website. To access their accounts, customers of the bank must create an 8-digit password. It is your job to determine the password requirements for these accounts. Security guidelines state that for the website to be secure, the probability that an 8-digit password is guessed on one try must be less than 1/60^8, assuming all passwords are equally likely.
Your job is to use the probability techniques you have learned in this chapter to decide what requirements a customer must meet when choosing a password, including what sets of characters are allowed, so that the website is secure according to the security guidelines.
2. Answering the Question
a. What password requirements would you set? What characters would be allowed?
You work in the security department of a bank’s website. To access their accounts, customers of the bank must create an 8-digit password. It is your job to determine the password requirements for these accounts. Security guidelines state that for the website to be secure, the probability that an 8-digit password is guessed on one try must be less than 1/60^8, assuming all passwords are equally likely.
Your job is to use the probability techniques you have learned in this chapter to decide what requirements a customer must meet when choosing a password, including what sets of characters are allowed, so that the website is secure according to the security guidelines.
3. For additional security, each customer creates a 5-digit PIN (personal identification number). The table on the right shows the 10 most commonly chosen 5-digit PINs. From the table, you can see that more than a third of all 5-digit PINs could be guessed by trying these 10 numbers. To discourage customers from using predictable PINs, you consider prohibiting PINs that use the same digit more than once.
b. Would you decide to prohibit PINs that use the same digit more than once? Explain.
2. How many possible variations are there in Mozart's Musical Dice Game minuet? Explain.
5. Use technology to randomly select two numbers from 1 to 6. Find the sum and subtract 1 to obtain a total.
a. What is the theoretical probability of each total from 1 to 11?
b. Use this procedure to select 100 totals from 1 to 11. Tally your results and compare them with the probabilities in part (a).
Cards In Exercises 59-62, you are dealt a hand of five cards from a standard deck of 52 playing cards.
62. Find the probability of being dealt three of a kind (the other two cards are different from each other).
In Exercises 41-44, perform the indicated calculation.
42. 8P6
In Exercises 41-44, perform the indicated calculation.
44. (5C3)/(10C3)
4. The table on the left shows the secondary school student enrollment levels (in thousands by grade) in Oklahoma and Texas schools in a recent year. (Source: U.S. Nation
for Education Statistics)
A student in one of the indicated grades and states is randomly selected. Find the probability of selecting a student who
d. is enrolled in Texas, given that the student is in twelfth grade.
7. There are 16 students giving final presentations in your history course.
b. Presentation subjects are based on the units of the course. Unit B is covered by three students, Unit C is covered by five students, and Units A and D are each covered by four students. How many presentation orders are possible when presentations on
the same unit are indistinguishable from each other?
Social Security Numbers
A Social Security number is used to identify each resident of the United States uniquely. The number is of the form xxx-xx-xxxx, where each x is a digit from 0 to 9.
b. What is the probability of correctly guessing the Social Security number of the president of the United States?
In Problems 11–18, find the value of each permutation.
9P4
[NW] Arranging Songs Suppose Dan is going to create a Spotify playlist with 12 songs. In how many ways can the 12 songs be played without repetition?