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ABCDEFGH
Ab → no T together CD → no together
Required probability is-
('4C3 +2* 4C2+ 4C2+2*2*4C1)/8C3
4C3- choosing any 3 from efgh,
2x 4c2- choosing any one from ab and CD and 2 from remaining 4
2x2* 4c1-
Ch oosing any one from ab, any one from CD, and any from EFGH
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From these 8 individuals (12345678) - we can have a total of 8C3 selections.
Now, let's reckon the incompatibles (12X) we must remove such selections and X has 6 possibilities.
At the same time there are other two incompatibles, by a similar reasoning, we will have 6 more possibilities.

The Probability will be = (8C3 -6-6)/(8C3)= 44/56=11/14
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This is a classic probablity question:
you want to do the total - bad outcome.
Total is (8x7x6)/(3x2x1) = 56. the 3x2x1 removes duplicaates.

Then chose aly and ben plus any of the other 6, so thats 1x1x6, repeat twice for the other pair. total bad pairs = 12.
56-12 = 44.
44/56 = 11/14.
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Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.
Let's take 2 cases when A - B and C - D are together.
A B _ = 6 cases possible
C D _ = 6 cases possible
In total, 12 cases of not valid committees

select 3 candidates out of 8 people will be 8C3 = 8!/3!5! = 56
probability of valid committees = (total possible - not valid)/total possible
= (56 - 12)/56
= 44/56 => 11/14
so X/Y = 11/14
X = 11, Y = 14
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Ways of selecting any 3 members (Y) = 8C3
Ways of selecting 3 members without conflict: [Select 3 from EFGH ]or [Select 1 from (AB) x Select 2 from EFGH ] or [ Select 1 from CD x Select 2 from EFGH] or [Select 1 from AB x Select 1 from CD x Select 1 from EFGH]
or, X = 4C3 + ( 2C1 x 4C2) + (2C1 x 4C2) + (2C1 x 2C1 x 4C1)
or, Solving Y = 56 & X= 44, X/Y = 11/14
or X= 11, Y=14
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Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.

Attachments

File comment: So whenever i get probability question i find out the total number of ways

To form a committee good or bad (by good i mean no non- compatible pairs are present and committee is formed successfully; bad is incompatible pairs are present and formation of committee is failed lol)

so total ways = 3 choose 9 = 56
Lets say Ally and Ben are present so there are 6 waya with remaining 6 candidates
similarly with Cam and Dan 6 ways

so total incompatible or bad committe ways =

6+6 =12 ways


P of a bad committee is 12/56

P of a good committee is 1 - 12/56 =0.786 or 44/56 or 11/14

so X is 11
and Y is 14

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8C3 = 56. It's the total number of ways to select 3 people from an 8-person group.
Now the challenge comes when you have to select a group which is not a valid committee. That group consists either of an A-B pair or a C-D pair.
Here the order doesn't matter therefore we should not use the permutation formula, which means that (A,B,D) is the same as (B,D,A).
[(A,B), any number x] can be arranged in 2! ways, that is, 2 ways. Same goes for C-D pair. Therefore there are 4 ways we cannot make a committee.
The favorable number of outcomes is 56 - 4 = 52. The total number of outcomes is 56.
Answer = 52/56 = 13/14
Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.
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Total Cases = 8C3 = 56
Now A-B & C-D combinations cannot be in the same team
So possible combinations are-
1. Either of A-B or C-D and 2 from remaining 4 = (2C1*2)*4C2 = 24
2. Either of A-B and either of C-D and 1 from remaining 4 = 2C1*2C1*4C1 = 16
3. None A-B-C-D and all from remaining 4 members = 4C3 = 4

So sum of possiblities = 24+16+4 = 44

So probability is 44/56 = 11/14


Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.
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We have to choose 3 people from 8 member pool. This can be done in 8C3 = 56 ways

Counting the number of allowed committees will be tedious. So lets count the number of invalid committees and subtract from the total possible number of committees.

With A and B in the team, and one person from the rest of 6 members, we can create the committee in 6 ways.

Similarly, with C and D in the team, we can choose one member from the rest in 6 ways.

With both incompatible pairs, A, B, C, D - we cannot create a team as we need only 3 members.

Subtracting the 12 invalid committees, we get 44 ways of valid committees.

The probability is thus 44/56 = 11/14 ways.
Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.
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11/14
so we can do this by
fixing A,B and then selecting 1 from remaining 6 thats 6 ways
similarly for C,D which have both of them selected 6 ways (c,d,_,_,_,_,_,_)
also totally selecting 3 from 8 people can be done in 8C3 ways =56
so 1-12/56(probability we select ab and cd in team )
44/56=11/14
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We need to find the total number of invalid cases:

Case 1: A and B both are selected
Number of outcomes: Out of the 3 people A and B are already selected so the remaining 1 spot can be filled in 6C1 ways which is 6.

Case2: C and D both are selected
Number of outcomes: Out of the 3 people C and D are already selected so the remaining 1 spot can be filled in 6C1 ways which is 6.

Total unfavourable cases: 6 + 6 = 12.
Total number of cases: 3 people need to selected from 8 people this can be done in 8C3 ways which is 56.

Probability of valid cases: 1 - invalid/total
Hence 1 - 12/56 = 44/56 = 11/14
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total ways of selecting : 8c3 = 56, When both A&B are selected, no. of ways of selecting remaining is 6. when both C&D are selected, no of ways of selecting remaining is 6. So total 12 invalid combinations. Favourable/total = 44/56, 11/14.
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Total number of possible committees are 8C3 = 56
Committees with both aly and ben 2C2 x 6C1 = 6
Committees with both cam and dan 2C2 x 6C1 = 6
Total invalid committees therefore are = 6+6= 12
So no. Of valid committees are 56-12= 44

Therefore fraction of valid committees or x/y = 44/56= 11/14
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Answer: x is 11 and y is 14

Explanation:

The total number of combinations is 8C3 =56

There are 12 combinations of A and B, or C and D are both serve on the committee together.

So the probability is:
(56-12)/56
=44/56
=11/14

Bunuel
A company is forming a three-person leadership committee from a pool of eight qualified candidates: Aly, Ben, Cam, Dan, Emi, Fay, Gia, and Hal. Due to conflicts of interest, two pairs of candidates are incompatible: Aly and Ben cannot both serve on the committee together, and Cam and Dan cannot both serve on the committee together. A committee is considered valid only if its three members do not include either of these pairs of incompatible candidates.

Consider the following incomplete sentence:

If three candidates are chosen at random, the probability that the selected candidates form a valid committee is X / Y , where the fraction is expressed in simplest form.

Select for X and Y values that are consistent with the information provided. Make only two selections, one in each column.
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Total ways to select 3 members from 8 members => 8C3 =8!/3!*5! = (8*7*6)/(3*2) = 56
Cases to exclude- Case 1 : when Aly and Ben are together A,B, 6 choices remaining. Same when Cam and Dan are together.
6+6 = 12 cases to exclude.

Probability of a valid committee is (56-12)/56 = 44/56 = 11/14
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Tried calculating valid combinations but did not work out. So calculating invalid combinations.

Invalid combo 1: When A and B are in the group of 3. 3rd place can be filled by one of the 6 remaining folks, so 6 possibilities.

Invalid Combo 2: Same as 1 but this time with C and D. So another 6 possibilities.

Total invalid possibilities - 6+6 = 12. so total invalid prob = 12/8C3 which is 3/14
So total valid probability is 1 - 3/14 = 11/14 (X = 11, Y = 14)
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as per question, total = 8c3 = 56 and since they mentioned about valid, let's assume calculating AB and CD tog
which is 6C1 and 6C1 respectively if considered.
Hence , not tog = 56- (6+6) = 44
fraction = x/y = 44/56 = 11/14
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