Combinations Math Problem: Finding Possible Pairings with 10 Women and 12 Men

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In summary, there are 252 possible pairings when choosing 5 women and 5 men from sets of 10 and 12, respectively. This is calculated by multiplying the binomial coefficients for choosing 5 men and 5 women, and then considering the different ways of arranging them. However, since the order of the pairs does not matter, the final answer is divided by 2! to account for the repeated combinations.
  • #1
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Homework Statement


there are 10 women and 12 men. 5 pairs are to be made, each pair having one man and one women. how many pairings are possible.

The Attempt at a Solution


first let's choose men and women from each set. there are ##{10 \choose 5}## women and ##{12 \choose 5}## men. now that we have these, what should i be thinking? i know the answer is ##{12 \choose 5} \times {10 \choose 5} \times 5!##. why multiply by the ##5!##?

thanks!
 
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  • #2
Your binomial coefficients give the number of ways of choosing 5 women and 5 men. Now you have to figure out how many different pairs you can make with them.
 
  • #3
In other words once you have chose the five men and five woman, how many ways can you order them man,woman,man,woman, etcetera...
 
  • #4
LCKurtz said:
Your binomial coefficients give the number of ways of choosing 5 women and 5 men. Now you have to figure out how many different pairs you can make with them.

how many different pairs...this seems tough. well, I'm thinking of 5 positions. first, for the men there are ##5!## different ways to seat them. now for the women, there are also ##5!## ways to sit them. i think the answer is now ##5!+5!##. however, since women/man is the same as man/women, we divide by ##2!##?

is this correct?

thanks!
 
  • #5
joshmccraney said:
how many different pairs...this seems tough. well, I'm thinking of 5 positions. first, for the men there are ##5!## different ways to seat them. now for the women, there are also ##5!## ways to sit them. i think the answer is now ##5!+5!##. however, since women/man is the same as man/women, we divide by ##2!##?

is this correct?

thanks!

No. Normally counting like that you would multiply the two numbers. But that isn't the correct analysis for this problem anyway. Look at it this way. All the men are seated and it doesn't matter what order. Now how many ways can you seat the ladies on their laps? There are your pairs.
 
  • #6
Alright this is great! Makes perfect sense! Thanks!
 

Related to Combinations Math Problem: Finding Possible Pairings with 10 Women and 12 Men

1. How many possible pairings can be made with 10 women and 12 men?

The number of possible pairings can be calculated using the combination formula, which is nCr = n! / (r! * (n-r)!). In this case, n = 22 (10 women + 12 men) and r = 2 (since we are pairing 2 individuals at a time). Therefore, the number of possible pairings is 22C2 = 22! / (2! * (22-2)!) = 231 possible pairings.

2. Can each person be paired with more than one partner?

No, in this scenario, each person can only be paired with one partner at a time. This is because we are considering pairings as exclusive and not allowing for repetition.

3. How is this type of problem different from a permutation problem?

In a combination problem, the order of the elements does not matter. For example, pairing person A with person B is considered the same pairing as pairing person B with person A. In a permutation problem, the order does matter. So, pairing person A with person B would be considered a different pairing from pairing person B with person A.

4. Can the number of pairings change if there are more or less men or women?

Yes, the number of pairings will change depending on the number of men and women. The number of possible pairings is directly dependent on the total number of individuals in the group.

5. How can this type of problem be applied in real-life situations?

This type of problem can be applied in situations where we need to consider all possible combinations of a group of people. For example, it can be used in speed dating events where organizers need to consider all possible pairings of men and women. It can also be used in creating seating arrangements for events or assigning group projects in a class.

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