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Hand shaking (again)

  1. Apr 28, 2005 #1


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    this is possibly the only interesting hand shaking question i know of:

    5 couples go to a party. at the party everyone shakes hands with every one they dont know. (note: its not a blind date thing, i mean everyone knows their spouse)

    at the end, Bill, the known loser, asks everyone how many times they shook hands. after, he promptly forgets who told him what number, but he knows that as an answer he got every number from 0 to 8 inclusive. he doesnt ask himself.

    how many times did his spouse shake hands?
  2. jcsd
  3. Apr 29, 2005 #2
    Excellent one. Is it 4?

    Logic is in white.

    Persons with 0 and 8 handshakes are one couple(otherwise the person with 8 handshakes can have maximum 7 handshakes). Persons with 1 and 7 handshakes are one couple. Otherwise person with 7 handshake can have maximum 6 handshakes (excluding his/her, his/her spouse, person with 0 handshakes and person with 1 handshake(person with one handshake already did it with person with 8 handshakes)). So are 2,6 and 3,5 are couples.

    If I am correct, thanks for sharpening my rusting brain. :redface:
  4. Apr 29, 2005 #3


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    exactly! good work. it is one of the better logic/handshake ones isnt it :)

    I especially like how when you first hear the question its like whoa - whos Bill.

    but then it makes sense. :wink:

    this is actually fun to ask people you know. some people get it right off, some need the hint that 0 and 8 are married, and some just cant do it even with the hint.
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