Re: There are 7 married couples (14 people total).
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02 Feb 2026, 10:06
1. The Total Number of Outcomes
The number of ways to choose 8 people out of 14 is given by the combination formula $\(\binom{n}{k}\)$ :
$$
\(\binom{14}{8}=\frac{14!}{8!6!}=3003\)
$$
2. The Number of Successful Outcomes
We need to select exactly $\(\mathbf{3}\)$ couples and then $\(\mathbf{2}\)$ individuals who are the same gender but not part of a 4th couple.
Step A: Choose the $\mathbf{3}$ couples There are $\(\mathbf{7}\)$ couples available. We choose 3:
$$
\(\binom{7}{3}=35 \text { ways }\)
$$
Step B: Choose the remaining $\mathbf{2}$ people (Same Gender) We have $\(\mathbf{7}-\mathbf{3}=\mathbf{4}\)$ couples remaining ( 8 people: 4 men and 4 women). To ensure we don't accidentally pick a 4th couple, we must pick our 2 people from different remaining couples.
- Case 1: Two Men. We choose 2 couples out of the remaining 4, and take the man from each:
$$
\(\binom{4}{2}=6 \text { ways }\)
$$
- Case 2: Two Women. We choose 2 couples out of the remaining 4, and take the woman from each:
$$
\(\binom{4}{2}=6 \text { ways }\)
$$
Total ways to pick the 2 extra people: $6+6=12$ ways.
Step C: Calculate total successful combinations Multiply the choices together:
$$
\(35(\text { couples }) \times 12(\text { individuals })=420 \text { ways }\)
$$
3. Final Probability Calculation
The probability ( $P$ ) is the successful outcomes over the total outcomes:
$$
\(P=\frac{420}{3003}\)
$$
We can simplify this by dividing both numerator and denominator by 21 :
$$
\(P=\frac{20}{143}\)
$$