Combinatorics

Description: This quiz is designed to test your understanding of Combinatorics, a branch of mathematics that deals with counting and arranging objects.
Number of Questions: 14
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Tags: combinatorics counting arrangements permutations combinations
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In a group of 10 people, how many ways can you select a committee of 5 people?

  1. 252

  2. 120

  3. 240

  4. 300


Correct Option: A
Explanation:

This is a combination problem. The formula for combinations is C(n, r) = n! / (n - r)!. In this case, n = 10 and r = 5, so C(10, 5) = 10! / (10 - 5)! = 10! / 5! = 252.

A bag contains 6 red balls, 4 blue balls, and 2 green balls. How many ways can you select 3 balls from the bag if you must select at least one ball of each color?

  1. 120

  2. 144

  3. 168

  4. 192


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 1 red ball from 6 red balls, which can be done in 6 ways. Then, you need to select 1 blue ball from 4 blue balls, which can be done in 4 ways. Finally, you need to select 1 green ball from 2 green balls, which can be done in 2 ways. So, the total number of ways is 6 * 4 * 2 = 144.

A company has 10 employees. In how many ways can the company select a team of 3 employees to attend a conference?

  1. 120

  2. 720

  3. 1200

  4. 2520


Correct Option: A
Explanation:

This is a permutation problem. The formula for permutations is P(n, r) = n! / (n - r)!. In this case, n = 10 and r = 3, so P(10, 3) = 10! / (10 - 3)! = 10! / 7! = 120.

A club has 15 members. In how many ways can the club select a president, a vice president, and a secretary?

  1. 2730

  2. 455

  3. 2220

  4. 3645


Correct Option: C
Explanation:

This is a permutation problem with repetitions. The formula for permutations with repetitions is P(n, r) = n^r. In this case, n = 15 and r = 3, so P(15, 3) = 15^3 = 2220.

A box contains 10 red balls, 12 blue balls, and 15 green balls. How many ways can you select 5 balls from the box if you must select at least 2 red balls?

  1. 2380

  2. 3003

  3. 4095

  4. 5005


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 2 red balls from 10 red balls, which can be done in C(10, 2) = 45 ways. Then, you need to select 3 balls from the remaining 27 balls (12 blue balls + 15 green balls), which can be done in C(27, 3) = 2925 ways. So, the total number of ways is 45 * 2925 = 3003.

A committee of 5 people is to be selected from a group of 10 people. How many ways can this be done if 2 particular people must be on the committee?

  1. 252

  2. 120

  3. 300

  4. 420


Correct Option: A
Explanation:

This is a combination problem with restrictions. First, you need to select the 2 particular people from the group of 10 people, which can be done in C(10, 2) = 45 ways. Then, you need to select 3 more people from the remaining 8 people, which can be done in C(8, 3) = 56 ways. So, the total number of ways is 45 * 56 = 252.

A company has 12 employees. In how many ways can the company select a team of 4 employees to work on a project if 2 particular employees cannot work together?

  1. 360

  2. 495

  3. 630

  4. 792


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select the 2 particular employees who cannot work together from the group of 12 employees, which can be done in C(12, 2) = 66 ways. Then, you need to select 4 employees from the remaining 10 employees, which can be done in C(10, 4) = 210 ways. So, the total number of ways is 66 * 210 = 495.

A bag contains 8 red balls, 6 blue balls, and 4 green balls. How many ways can you select 4 balls from the bag if you must select at least 1 ball of each color?

  1. 336

  2. 420

  3. 504

  4. 588


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 1 red ball from 8 red balls, which can be done in 8 ways. Then, you need to select 1 blue ball from 6 blue balls, which can be done in 6 ways. Finally, you need to select 1 green ball from 4 green balls, which can be done in 4 ways. So, the total number of ways is 8 * 6 * 4 = 420.

A club has 10 members. In how many ways can the club select a president, a vice president, and a secretary if the same person cannot hold more than one office?

  1. 720

  2. 2520

  3. 5040

  4. 10080


Correct Option: A
Explanation:

This is a permutation problem without repetitions. The formula for permutations without repetitions is P(n, r) = n!. In this case, n = 10 and r = 3, so P(10, 3) = 10! = 720.

A company has 15 employees. In how many ways can the company select a team of 5 employees to attend a conference if the team must include at least 2 women?

  1. 1050

  2. 1260

  3. 1470

  4. 1680


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 2 women from the group of 15 employees, which can be done in C(7, 2) = 21 ways. Then, you need to select 3 more employees from the remaining 13 employees, which can be done in C(13, 3) = 286 ways. So, the total number of ways is 21 * 286 = 1260.

A bag contains 10 red balls, 12 blue balls, and 15 green balls. How many ways can you select 5 balls from the bag if you must select at least 1 red ball and at least 1 blue ball?

  1. 3960

  2. 4320

  3. 4680

  4. 5040


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 1 red ball from 10 red balls, which can be done in 10 ways. Then, you need to select 1 blue ball from 12 blue balls, which can be done in 12 ways. Finally, you need to select 3 more balls from the remaining 27 balls (15 green balls + 10 red balls + 12 blue balls), which can be done in C(27, 3) = 2925 ways. So, the total number of ways is 10 * 12 * 2925 = 4320.

A committee of 5 people is to be selected from a group of 12 people. How many ways can this be done if 2 particular people must be on the committee and they must be seated next to each other?

  1. 1320

  2. 1560

  3. 1800

  4. 2040


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select the 2 particular people who must be on the committee and seated next to each other, which can be done in 2 ways. Then, you need to select 3 more people from the remaining 10 people, which can be done in C(10, 3) = 120 ways. So, the total number of ways is 2 * 120 = 1560.

A company has 18 employees. In how many ways can the company select a team of 6 employees to work on a project if 3 particular employees cannot work together?

  1. 5985

  2. 6720

  3. 7455

  4. 8190


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select the 3 particular employees who cannot work together from the group of 18 employees, which can be done in C(18, 3) = 816 ways. Then, you need to select 6 employees from the remaining 15 employees, which can be done in C(15, 6) = 5005 ways. So, the total number of ways is 816 * 5005 = 6720.

A bag contains 12 red balls, 10 blue balls, and 8 green balls. How many ways can you select 5 balls from the bag if you must select at least 2 red balls and at least 2 blue balls?

  1. 2520

  2. 2880

  3. 3240

  4. 3600


Correct Option: B
Explanation:

This is a combination problem with restrictions. First, you need to select 2 red balls from 12 red balls, which can be done in C(12, 2) = 66 ways. Then, you need to select 2 blue balls from 10 blue balls, which can be done in C(10, 2) = 45 ways. Finally, you need to select 1 more ball from the remaining 20 balls (8 green balls + 12 red balls + 10 blue balls), which can be done in 20 ways. So, the total number of ways is 66 * 45 * 20 = 2880.

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