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and some er. SATURDAY night maths...

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  • and some er. SATURDAY night maths...

    I am at the moment reading a book given to me five! years ago, the excellent Simon Singh's book about the Fermat impossibility (or whatever). It keeps you in a spell, I highly recommend it, and anyone can read it, requires no mathematical skills, and even presents a mathematical history dating back to Pythagoras...

    Just to stress your braincells, could you tell me (my own quick estimate was a true embarassment) with no previous knowledge and without referencing or so:

    Imagine a soccer game, 11 player on each team and a referee. What is the probability that any two people on the field have the same birthdays?

    Gee, I am looking forward to this one...will of course provide answer and motivation. Good luck!
    Last edited by Dicke Bertha; 20 Mar 04, 12:50.
    "You can't change the rules in the middle of the game."
    "Hey, you just made that rule up."


    Heil Dicke Bertha!

  • #2
    Is it 1 in 365?

    Seems too obvious...


    Goblin
    Mega Campaign Screaming Eagles and Das Reich Design Team Member
    DAS REICH CAMPAIGN, and THE SPWaW ICON GUIDE AVAILABLE AT: The SP:WaW Depot
    In difficult ground, press on. In encircled ground, devise strategems. In death ground, fight.

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    • #3
      Originally posted by Goblin
      Is it 1 in 365?

      Seems too obvious...


      Goblin
      it does doesn't it, sorry wrong answer (sound of toilet flushing)
      "You can't change the rules in the middle of the game."
      "Hey, you just made that rule up."


      Heil Dicke Bertha!

      Comment


      • #4
        1 in 16?

        Goblin- A Goblin is out of guesses
        Mega Campaign Screaming Eagles and Das Reich Design Team Member
        DAS REICH CAMPAIGN, and THE SPWaW ICON GUIDE AVAILABLE AT: The SP:WaW Depot
        In difficult ground, press on. In encircled ground, devise strategems. In death ground, fight.

        Comment


        • #5
          He Goblin
          sorry again, not correct.
          Are you guessing wildly here, or devising new maths?
          "You can't change the rules in the middle of the game."
          "Hey, you just made that rule up."


          Heil Dicke Bertha!

          Comment


          • #6
            Here in USA we have multiple choice tests. So give us some answers with the correct one included and eventually we'll guess the right one (maybe even in the first try).

            I know, in Europe they examine by malking you walk up to the teacher in front of class and give a verbal answer. Most embarassing.

            Mutliple choice is the American way.

            "Artillery adds dignity to what would otherwise be a ugly brawl."
            --Frederick II, King of Prussia

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            • #7
              Originally posted by Dicke Bertha
              He Goblin
              sorry again, not correct.
              Are you guessing wildly here, or devising new maths?

              No, I divided 23 into 365, and came out with 15.9 or roughly a 6% chance. Its been a long time since I was in math class...


              Goblin
              Mega Campaign Screaming Eagles and Das Reich Design Team Member
              DAS REICH CAMPAIGN, and THE SPWaW ICON GUIDE AVAILABLE AT: The SP:WaW Depot
              In difficult ground, press on. In encircled ground, devise strategems. In death ground, fight.

              Comment


              • #8
                Originally posted by Dicke Bertha
                Imagine a soccer game, 11 player on each team and a referee. What is the probability that any two people on the field have the same birthdays?
                Approximately 1 in 2.

                I'm not really interested in doing the math accurately, so approximate is all you get :P
                "Experience should teach us to be most on our guard to protect liberty when the government’s purposes are beneficent. Men born to freedom are naturally alert to repel invasion of their liberty by evil-minded rulers. The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding."

                – Associate Justice Louis D. Brandeis, Olmstead vs. United States.

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                • #9
                  1 in 5792?

                  Thanks for the headache.


                  Goblin
                  Mega Campaign Screaming Eagles and Das Reich Design Team Member
                  DAS REICH CAMPAIGN, and THE SPWaW ICON GUIDE AVAILABLE AT: The SP:WaW Depot
                  In difficult ground, press on. In encircled ground, devise strategems. In death ground, fight.

                  Comment


                  • #10
                    First find the probability that all have different birthdays, then subtract that from 1.

                    Also, assume that we are only talking about 365 day years (no leap years), and that there are no twins, triplets, et cetera, on the field. Finally, only consider the date, and not the year of birth.

                    Take any one person on the field and note their birthday. The probability that the next person chosen will have a different birthday is (364/365). The probability that the third person has a birthday different from the first two is (363/365). And so on. For 23 people we have the following as a probability for all having different birthdays:
                    (364/365)*(363/365)*...*(343/365) = approx (1.16 x 10^56)/(2.35 x 10^56) = approx 0.49.

                    So, 1-(.49) = .51 = approx one half, like MikeJ said!

                    ...in case anyone doubted him...
                    I have no problem at all with being proved wrong. Especially when being proved wrong leaves the world a better place, than being proved right...

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                    • #11


                      It is wohl probably no wonder why people such as MikeJ and Jam are feared opponents in TOAW? The correct answer, as cleverly put forward but those mentioned (and specially honorary mention to Goblin for harassing the grey cells, and who'd have gotten it in 365 days, given one try a day (? has to be checked by Jam et Mike though)) is 50,7%.

                      As an engineer, I am blushing as I tell you that my guess was totally wrong, if I remember around 18%. Goblin, I'll buy you a beer, and we can plan our revenge on mathematicians.

                      Jam's explanation is correct, the first player can be paired with 22 other, the next with 21 players, the next with 20 etc. The total pairs = 253.
                      The principle for probability is multiplication of the individual cases and will yield the 50,7%.
                      "You can't change the rules in the middle of the game."
                      "Hey, you just made that rule up."


                      Heil Dicke Bertha!

                      Comment


                      • #12
                        Originally posted by MonsterZero
                        Here in USA we have multiple choice tests. So give us some answers with the correct one included and eventually we'll guess the right one (maybe even in the first try).

                        I know, in Europe they examine by malking you walk up to the teacher in front of class and give a verbal answer. Most embarassing.

                        Mutliple choice is the American way.

                        No can do

                        your fellas solved it grandly old style
                        "You can't change the rules in the middle of the game."
                        "Hey, you just made that rule up."


                        Heil Dicke Bertha!

                        Comment


                        • #13
                          Originally posted by Dicke Bertha
                          As an engineer, I am blushing as I tell you that my guess was totally wrong,
                          Eh don't be. Nobody really uses that crap anyways, except maybe insurance companies :P.

                          I had to take a statistics class as part of my computer systems program and I've not had any significant practical application for any of it. If I ever do, it's not like I ever needed to remember it. I just go to the library and pickup a stats book (or just search online) and voila, everything I need to write algorithms/business logic.

                          The class wasn't a total loss though. I got a lot of work for my other classes done in it .
                          "Experience should teach us to be most on our guard to protect liberty when the government’s purposes are beneficent. Men born to freedom are naturally alert to repel invasion of their liberty by evil-minded rulers. The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding."

                          – Associate Justice Louis D. Brandeis, Olmstead vs. United States.

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                          • #14
                            JAMiAMs avatars are getting out of control

                            "Artillery adds dignity to what would otherwise be a ugly brawl."
                            --Frederick II, King of Prussia

                            Comment


                            • #15
                              Full ACK, MonsterZero!
                              Maj. Reismann: "Kill every officer in sight!"
                              soldier: "Ours or theirs?"

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