Finding Number of Handshakes in a Party

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SUMMARY

The problem involves determining the number of handshakes at a party attended by n couples, where no one shakes hands with their spouse or themselves. The hostess discovers 2n + 1 unique handshake counts among the guests. By analyzing specific cases for n = 3 and n = 4, a general pattern can be established to solve for any positive integer n. The solution requires understanding the constraints of the handshake problem and deriving a formula based on these observations.

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Homework Statement


A couple invites n 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 2n + 1 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 n = 3 and then n = 4, and then find a general pattern that works for an arbitrary positive integer n. 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 n=..." is over my head. So far, I wrote that there are n+1 total couples (including the host), so there are 2(n+1) = 2n+2 individuals. I don't know where to go from here.

Any ideas? As always, much appreciated.
 
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Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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