Finding Number of Handshakes in a Party

  • Thread starter SithsNGiggles
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In summary, the problem presented is about a couple inviting n couples to a party where some people shake hands with each other but not with their own spouse or themselves. The hostess asks each guest (including her husband) how many individuals they shook hands with, and amazingly comes up with 2n+1 different numbers. The task is to determine how many people the hostess and host shook hands with, which can be solved by finding a general pattern for an arbitrary positive integer n.
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SithsNGiggles
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Homework Statement


A couple invites [itex]n[/itex] couples to a party. Upon arriving, some people shake hands with each other and some do not, but nobody shakes hands with one's own spouse or with oneself. After all the guests have arrived, the hostess asks each of her guests as well has her husband how many individuals the person shook hands with. Amazingly, she comes up with [itex]2n + 1[/itex] different numbers. The problem now is this: with how many people did the hostess shake hands, and with how many people did the host shake hands?

(Suggestion: Work this out first for [itex]n = 3[/itex] and then [itex]n = 4[/itex], and then find a general pattern that works for an arbitrary positive integer [itex]n[/itex]. You will need to prove that it does indeed work.)

Homework Equations



The Attempt at a Solution


Not much was done on my part; I don't know how to approach this. The suggestion as to "work it out for [itex]n=...[/itex]" is over my head. So far, I wrote that there are [itex]n+1[/itex] total couples (including the host), so there are [itex]2(n+1) = 2n+2[/itex] individuals. I don't know where to go from here.

Any ideas? As always, much appreciated.
 
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  • #2

FAQ: Finding Number of Handshakes in a Party

What is the formula for finding the number of handshakes?

The formula for finding the number of handshakes in a group of n people is n(n-1)/2. This formula accounts for the fact that each person will shake hands with every other person in the group, except for themselves.

How is the number of handshakes affected by the number of people in the group?

The number of handshakes is directly proportional to the number of people in the group. This means that as the number of people increases, the number of handshakes will also increase. For example, a group of 10 people will have 45 handshakes, while a group of 20 people will have 190 handshakes.

Is there a limit to the number of handshakes in a group?

Yes, there is a limit to the number of handshakes in a group. The maximum number of handshakes can be achieved when every person in the group shakes hands with every other person. This is when the number of handshakes is equal to n(n-1)/2, where n is the number of people in the group.

Can the number of handshakes be calculated for a group where people only shake hands with certain individuals?

Yes, the number of handshakes can still be calculated for a group where people only shake hands with certain individuals. The formula for finding the number of handshakes remains the same, but only includes the number of people who are actually shaking hands with each other.

Why is it important to know the number of handshakes in a group?

Knowing the number of handshakes in a group can be important for event planning, networking, and understanding social dynamics. It can also be useful in mathematical and statistical analyses, as well as in certain scientific experiments and studies that involve human interactions.

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