Applications of Combinatorics

Description: This quiz covers various applications of combinatorics, including counting techniques, probability, and optimization.
Number of Questions: 15
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Tags: combinatorics counting techniques probability optimization
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In a group of 10 people, how many ways can we select a president, a vice president, and a secretary?

  1. 720

  2. 2520

  3. 5040

  4. 7560


Correct Option: A
Explanation:

We can use the multiplication principle. There are 10 ways to choose the president, 9 ways to choose the vice president, and 8 ways to choose the secretary. Therefore, the total number of ways is 10 x 9 x 8 = 720.

A company has 12 employees, and they want to form a committee of 4 people. How many different committees can be formed?

  1. 495

  2. 1188

  3. 2024

  4. 4096


Correct Option: A
Explanation:

We can use the combination formula. The number of ways to choose 4 people out of 12 is given by C(12, 4) = 12! / (12 - 4)! / 4! = 495.

A bag contains 6 red balls, 4 blue balls, and 2 green balls. If we randomly select 3 balls from the bag, what is the probability of getting exactly 2 red balls and 1 blue ball?

  1. 1/10

  2. 1/15

  3. 1/20

  4. 1/25


Correct Option: B
Explanation:

There are a total of 6 + 4 + 2 = 12 balls in the bag. The number of ways to choose 2 red balls out of 6 is C(6, 2) = 15. The number of ways to choose 1 blue ball out of 4 is C(4, 1) = 4. Therefore, the total number of ways to choose 2 red balls and 1 blue ball is 15 x 4 = 60. The probability of getting exactly 2 red balls and 1 blue ball is 60 / 12^3 = 1/15.

A company wants to assign 5 tasks to 3 employees. Each employee can be assigned any number of tasks. How many different assignments are possible?

  1. 125

  2. 243

  3. 343

  4. 512


Correct Option: B
Explanation:

We can use the stars and bars method. We have 5 tasks and 3 employees, so we can represent the assignment as a string of 5 stars and 2 bars. For example, the string ||* represents the assignment of the first task to the first employee, the second and third tasks to the second employee, and the fourth and fifth tasks to the third employee. The number of different assignments is equal to the number of ways to arrange 5 stars and 2 bars, which is given by C(5 + 2, 2) = 243.

A salesman has 10 customers to visit. In how many different orders can he visit them?

  1. 10!

  2. 9!

  3. 8!

  4. 7!


Correct Option: A
Explanation:

The salesman can visit the customers in any order, so we can use the permutation formula. The number of different orders is given by P(10, 10) = 10!.

A company has 10 job openings. They receive 20 applications. How many ways can they select 10 applicants to fill the job openings?

  1. 184756

  2. 264240

  3. 362880

  4. 484320


Correct Option: A
Explanation:

We can use the combination formula. The number of ways to choose 10 applicants out of 20 is given by C(20, 10) = 20! / (20 - 10)! / 10! = 184756.

A survey asks respondents to select their favorite color from a list of 5 colors. How many different ways can the respondents answer the question?

  1. 5

  2. 10

  3. 15

  4. 20


Correct Option: A
Explanation:

Each respondent can choose only one color, so the number of different ways to answer the question is equal to the number of colors, which is 5.

A company has 10 employees, and they want to form a team of 5 people to work on a project. How many different teams can be formed if each employee can be on only one team?

  1. 252

  2. 300

  3. 360

  4. 420


Correct Option: A
Explanation:

We can use the combination formula. The number of ways to choose 5 people out of 10 is given by C(10, 5) = 10! / (10 - 5)! / 5! = 252.

A bag contains 10 red balls, 8 blue balls, and 6 green balls. If we randomly select 4 balls from the bag, what is the probability of getting at least 1 red ball?

  1. 1/2

  2. 2/5

  3. 3/5

  4. 4/5


Correct Option: D
Explanation:

The probability of getting at least 1 red ball is equal to 1 minus the probability of getting no red balls. The probability of getting no red balls is given by (8/24)^4 = 1/256. Therefore, the probability of getting at least 1 red ball is 1 - 1/256 = 4/5.

A company has 12 employees, and they want to form a committee of 3 people. How many different committees can be formed if the president of the company must be on the committee?

  1. 220

  2. 286

  3. 330

  4. 396


Correct Option: A
Explanation:

We can first choose the president of the company, which can be done in 1 way. Then, we can choose the other 2 members of the committee from the remaining 11 employees, which can be done in C(11, 2) = 55 ways. Therefore, the total number of different committees is 1 x 55 = 220.

A survey asks respondents to select their favorite sport from a list of 10 sports. How many different ways can the respondents answer the question if they can select more than one sport?

  1. 10

  2. 55

  3. 252

  4. 1024


Correct Option: D
Explanation:

Each respondent can choose any number of sports from the list, so the number of different ways to answer the question is equal to 2^10 = 1024.

A company has 10 job openings. They receive 20 applications. How many ways can they select 10 applicants to fill the job openings if each applicant can be selected for only one job?

  1. 184756

  2. 264240

  3. 362880

  4. 484320


Correct Option: A
Explanation:

We can use the combination formula. The number of ways to choose 10 applicants out of 20 is given by C(20, 10) = 20! / (20 - 10)! / 10! = 184756.

A bag contains 10 red balls, 8 blue balls, and 6 green balls. If we randomly select 4 balls from the bag, what is the probability of getting exactly 2 red balls, 1 blue ball, and 1 green ball?

  1. 1/10

  2. 1/15

  3. 1/20

  4. 1/25


Correct Option: C
Explanation:

There are a total of 10 + 8 + 6 = 24 balls in the bag. The number of ways to choose 2 red balls out of 10 is C(10, 2) = 45. The number of ways to choose 1 blue ball out of 8 is C(8, 1) = 8. The number of ways to choose 1 green ball out of 6 is C(6, 1) = 6. Therefore, the total number of ways to choose 2 red balls, 1 blue ball, and 1 green ball is 45 x 8 x 6 = 2160. The probability of getting exactly 2 red balls, 1 blue ball, and 1 green ball is 2160 / 24^4 = 1/20.

A company has 12 employees, and they want to form a committee of 4 people. How many different committees can be formed if each employee can be on only one committee and the president of the company must be on the committee?

  1. 132

  2. 190

  3. 220

  4. 286


Correct Option: B
Explanation:

We can first choose the president of the company, which can be done in 1 way. Then, we can choose the other 3 members of the committee from the remaining 11 employees, which can be done in C(11, 3) = 165 ways. Therefore, the total number of different committees is 1 x 165 = 190.

A survey asks respondents to select their favorite color from a list of 5 colors. How many different ways can the respondents answer the question if they can select more than one color?

  1. 5

  2. 10

  3. 15

  4. 31


Correct Option: D
Explanation:

Each respondent can choose any number of colors from the list, so the number of different ways to answer the question is equal to 2^5 - 1 = 31.

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