A personality test assesses 32 key traits. These 32 traits are grouped into 4 domains - Cognition, Influence, Rapport and Planning - with each domain consisting of 8 traits. The test result for a person consists of his/her top 5 traits in ascending order of strength.

  1. (a)

    Find the number of different results that the personality test can produce.

  2. (b)

    Find the number of different results that can be produced with traits from at least 2 domains.

  3. (c)

    Find the number of different results that can be produced with at least one trait from each domain and neither of the top 2 traits are from the Cognition domain.

  4. (d)

    A result contains 2 particular traits from Rapport, 2 particular traits from Planning and 1 particular trait from Influence. Find the number of different possible results that can be produced with no consecutive traits from the same domain.

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

9(a)

1. Identify that the result is an ordered selection, so permutations are required.

The test result consists of 5 distinct traits selected from 32.
Since the 5 selected traits are presented in ascending order of their specific strengths for that person, the sequence of the traits matters (i.e. changing the order of the same 5 traits produces a different result). Therefore, this is a permutation problem.

2. Calculate the total number of permutations.

Number of different results=32P5\text{Number of different results} = {}^{32}P_5
=32×31×30×29×28= 32 \times 31 \times 30 \times 29 \times 28
=24165120= 24165120

Answer

2416512024165120

9(b)

1. Identify the total number of unrestricted results (from part a).

Since a result consists of 5 traits arranged in ascending order of strength, order matters.
Total results=32P5=24 165 120\text{Total results} = {}^{32}P_5 = 24\,165\,120

2. Calculate the number of results where all 5 traits belong to exactly 1 domain.

There are 4 domains, each with 8 traits. For all 5 traits to be from the same domain, we choose 1 domain, then arrange 5 of its 8 traits.
Results from exactly 1 domain=4×8P5\text{Results from exactly 1 domain} = 4 \times {}^{8}P_5
=4×6720=26 880= 4 \times 6720 = 26\,880

3. Use the complement method to find the number of results with traits from at least 2 domains.

Results from at least 2 domains=Total results−Results from exactly 1 domain\text{Results from at least 2 domains} = \text{Total results} - \text{Results from exactly 1 domain}
=24 165 120−26 880= 24\,165\,120 - 26\,880
=24 138 240= 24\,138\,240

Answer

24 138 24024\,138\,240

9(c)

1. Determine the required distribution of traits among the 4 domains.

Since the result consists of 55 traits and must include at least one trait from each of the 44 domains, exactly one domain must provide 22 traits, while the other three domains provide 11 trait each.
The valid domain distributions can be divided into two cases:

  • Case 1: The Cognition domain provides 22 traits.
  • Case 2: One of the other 33 domains provides 22 traits.

2. Calculate the number of valid results for Case 1 (Cognition provides 2 traits).

Number of ways to choose the traits (22 from Cognition, 11 from each of the other 33 domains):
1imes(82)imes(81)imes(81)imes(81)=14,3361 imes \binom{8}{2} imes \binom{8}{1} imes \binom{8}{1} imes \binom{8}{1} = 14,336
Out of these 55 chosen traits, exactly 33 are not from the Cognition domain.
The top 22 positions of the result cannot be from Cognition, so they must be filled by 22 of these 33 non-Cognition traits. The number of ways to arrange the top 22 positions is:
P(3,2)=3imes2=6P(3, 2) = 3 imes 2 = 6
The remaining 33 traits (which include the 22 Cognition traits and the unused non-Cognition trait) can be arranged in the bottom 33 positions in 3!=63! = 6 ways.
Number of valid results for Case 1 = 14,336imes6imes6=516,09614,336 imes 6 imes 6 = 516,096.

3. Calculate the number of valid results for Case 2 (a non-Cognition domain provides 2 traits).

There are 33 other domains (Influence, Rapport, Planning). Choose 11 to provide 22 traits ((31)=3\binom{3}{1} = 3 ways).
Number of ways to choose the traits:
3imes(82)imes(81)imes(81)imes(81)=43,0083 imes \binom{8}{2} imes \binom{8}{1} imes \binom{8}{1} imes \binom{8}{1} = 43,008
Out of these 55 chosen traits, exactly 44 are not from the Cognition domain.
The top 22 positions must be filled by 22 of these 44 non-Cognition traits. The number of ways to arrange the top 22 positions is:
P(4,2)=4imes3=12P(4, 2) = 4 imes 3 = 12
The remaining 33 traits can be arranged in the bottom 33 positions in 3!=63! = 6 ways.
Number of valid results for Case 2 = 43,008imes12imes6=3,096,57643,008 imes 12 imes 6 = 3,096,576.

4. Sum the results from both cases to find the total number of valid results.

The total number of valid results is the sum of the mutually exclusive results from Case 1 and Case 2:
Total=516,096+3,096,576=3,612,672\text{Total} = 516,096 + 3,096,576 = 3,612,672

Answer

3,612,672

9(d)

1. Find the total number of unconstrained arrangements for the 5 particular traits.

The 5 particular traits are distinct. The total number of unconstrained arrangements is:
5!=1205! = 120

2. Find the number of arrangements where traits from the same domain are consecutive.

If the 2 Rapport traits are consecutive, treat them as a single unit. We have 4 units in total, which can be arranged in 4!4! ways, and the 2 Rapport traits can be arranged within their unit in 2!2! ways.
Number of ways = 4!×2!=484! \times 2! = 48

Similarly, if the 2 Planning traits are consecutive, treat them as a single unit.
Number of ways = 4!×2!=484! \times 2! = 48

3. Calculate the number of arrangements where both the Rapport traits and the Planning traits are consecutive.

If both the 2 Rapport traits and 2 Planning traits are consecutive, treat each pair as a single unit. There are 3 units in total.
Number of ways = 3!×2!×2!=243! \times 2! \times 2! = 24

4. Use the principle of inclusion-exclusion to find the number of valid results.

Using the inclusion-exclusion principle, the number of arrangements with at least one consecutive pair from the same domain is:
48+48−24=7248 + 48 - 24 = 72

The number of valid results with no consecutive traits from the same domain is:
120−72=48120 - 72 = 48

Answer

4848

AI analysis — may contain mistakes.

Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.

More questions on this topic

  1. 1An amateur music composer is arranging a sequence of four musical notes followed by three beats. There are 7 possible no…
  2. 2Alice has 24 apples. In how many ways can she share them with Becky and Christ so that each of the three people has at l…
  3. 3Abby, Bridget, and four of their classmates will be seated in two rows of three for a group picture, as shown.If the sea…
  4. 4学校进行羽毛球选拔赛,每个参赛选手都要和其他所有选手赛一场.若有20人参赛,那么一共要进行 场选拔赛.
  5. 5Professor Chang has nine different language books lined up on a bookshelf: two Arabic, three German, and four Spanish. H…