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YAMP

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  • D David Stone

    Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


    The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

        a = 9.999999...
      10a = 99.999999...
    

    10a - a = 90
    9a = 90
    a = 10


    I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

    N Offline
    N Offline
    Nitron
    wrote on last edited by
    #11

    Nothing! 10 is an asymptote. It's like having:

      \_        \_
      |     1  |
    

    lim |y = --- | ====> y = 0
    | x | x-->(infinity)
    ¯ ¯

    - Nitron


    "Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

    N 1 Reply Last reply
    0
    • C Chris Richardson

      I don't think so. Multiplying it by 10 just shifts the decimal place right by one place. Chris Richardson Programmers find all sorts of ingenious ways to screw ourselves over. - Tim Smith

      T Offline
      T Offline
      Taka Muraoka
      wrote on last edited by
      #12

      Not true (I think :~) Multiplying by ten doesn't mean you play games with the symbols you use to write the number with, it means you add it ten times. Multiplying by 10 has the side-effect of "moving the decimal place" but: 1.234 * 10 = 12.340 if you want to keep the same number of decimal places. But this doesn't work if you have an infinite number of decimal places i.e. 9.999... * 10 != 99.999... Brit posted something where he used 1/infinity but you can't do that. Infinity is a concept, not a number.


      he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed) Awasu v0.4a[^]: A free RSS reader with support for Code Project.

      B 1 Reply Last reply
      0
      • D David Stone

        No it won't. The repeating nines will cancel each other out. If you have 3.99... - 3.99... doesn't that equal 0?


        I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

        N Offline
        N Offline
        Nick Seng
        wrote on last edited by
        #13

        not true, we have to assume that a and 10a have the same number of significant digits.What this means is that:

        a = 9.999 ... 999
        then
        10a = 99.99 ... 990
        thus
        10a - a = 89.99 ... 991

        Notorious SMC


        The difference between the almost-right word & the right word is a really large matter - it's the difference between the lightning bug and the Lightning Mark Twain
        Get your facts first, and then you can distort them as much as you please Mark Twain

        1 Reply Last reply
        0
        • N Nitron

          Nothing! 10 is an asymptote. It's like having:

            \_        \_
            |     1  |
          

          lim |y = --- | ====> y = 0
          | x | x-->(infinity)
          ¯ ¯

          - Nitron


          "Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

          N Offline
          N Offline
          Nick Seng
          wrote on last edited by
          #14

          X| X| X| X| Arrghh! I thought i left all those calculus back in College!! :Runs around in fear, remembering the nightmare of calculus: Notorious SMC


          The difference between the almost-right word & the right word is a really large matter - it's the difference between the lightning bug and the Lightning Mark Twain
          Get your facts first, and then you can distort them as much as you please Mark Twain

          1 Reply Last reply
          0
          • D David Stone

            Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


            The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

                a = 9.999999...
              10a = 99.999999...
            

            10a - a = 90
            9a = 90
            a = 10


            I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

            M Offline
            M Offline
            Michael Dunn
            wrote on last edited by
            #15

            I like this version: 0.9 / 9 = 0.1 1 / 9 = 0.1 Thus 0.9 = 1 :cool: --Mike-- When 900 years old you reach, look as good you will not. Hmm. 1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click! My really out-of-date homepage Sonork-100.19012 Acid_Helm

            1 Reply Last reply
            0
            • D David Stone

              Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


              The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

                  a = 9.999999...
                10a = 99.999999...
              

              10a - a = 90
              9a = 90
              a = 10


              I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

              P Offline
              P Offline
              peterchen
              wrote on last edited by
              #16

              If it goes on ad infinitum, 9.9... = 10. because 0.9... = 3* 1/3 = 1


              Those who not hear the music think the dancers are mad.  [sighist] [Agile]

              1 Reply Last reply
              0
              • D David Stone

                Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


                The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

                    a = 9.999999...
                  10a = 99.999999...
                

                10a - a = 90
                9a = 90
                a = 10


                I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

                G Offline
                G Offline
                geoneoration
                wrote on last edited by
                #17

                if your assumption is > a = 9.999999... > 10a = 99.999999... > 10a - a = 90 > 9a = 90 > a = 10 change a to 1.1111111... or 2.22222222... or 3.33333333... or ......... the result are the same that ten will equal 1.111111... or 2.222222... or 3.333333... or ...... :)

                Richard DeemingR 1 Reply Last reply
                0
                • D David Stone

                  Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


                  The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

                      a = 9.999999...
                    10a = 99.999999...
                  

                  10a - a = 90
                  9a = 90
                  a = 10


                  I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

                  K Offline
                  K Offline
                  KaRl
                  wrote on last edited by
                  #18

                  The infinite is not equal to (infinite - 1) ?


                  Angels banished from heaven have no choice but to become demons Cowboy Bebop

                  1 Reply Last reply
                  0
                  • D David Stone

                    Yet Another Math Puzzle Proof that playing math games with smart people isn't fun. If I gave that to my friends, they wouldn't be able to spot it for at least a little bit. Anyway, here's another one:


                    The following is what seems to be a mathematical proof that ten equals 9.999999.... What's wrong with it?

                        a = 9.999999...
                      10a = 99.999999...
                    

                    10a - a = 90
                    9a = 90
                    a = 10


                    I don't know whether it's just the light but I swear the database server gives me dirty looks everytime I wander past. -Chris Maunder Microsoft has reinvented the wheel, this time they made it round. -Peterchen on VS.NET

                    K Offline
                    K Offline
                    Kastellanos Nikos
                    wrote on last edited by
                    #19

                    It's the second line. You must see it as: a = 9.999999... 10a = 10(9.999999...) 10a - a = 9(9.999999...) - - - - - - - - - - - - - - - - - - Memory leaks is the price we pay \0 01234567890123456789012345678901234

                    1 Reply Last reply
                    0
                    • G geoneoration

                      if your assumption is > a = 9.999999... > 10a = 99.999999... > 10a - a = 90 > 9a = 90 > a = 10 change a to 1.1111111... or 2.22222222... or 3.33333333... or ......... the result are the same that ten will equal 1.111111... or 2.222222... or 3.333333... or ...... :)

                      Richard DeemingR Offline
                      Richard DeemingR Offline
                      Richard Deeming
                      wrote on last edited by
                      #20

                      No:

                      a = 1.111...
                      10a = 11.111...
                      10a - a = 10
                      9a = 10
                      a = 10 / 9 = 1 + 1/9

                      a = 2.222...
                      10a = 22.222...
                      10a - a = 20
                      9a = 20
                      a = 20 / 9 = 2 + 2/9

                      etc.


                      "These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

                      "These people looked deep within my soul and assigned me a number based on the order in which I joined" - Homer

                      1 Reply Last reply
                      0
                      • T Taka Muraoka

                        Not true (I think :~) Multiplying by ten doesn't mean you play games with the symbols you use to write the number with, it means you add it ten times. Multiplying by 10 has the side-effect of "moving the decimal place" but: 1.234 * 10 = 12.340 if you want to keep the same number of decimal places. But this doesn't work if you have an infinite number of decimal places i.e. 9.999... * 10 != 99.999... Brit posted something where he used 1/infinity but you can't do that. Infinity is a concept, not a number.


                        he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed) Awasu v0.4a[^]: A free RSS reader with support for Code Project.

                        B Offline
                        B Offline
                        Brit
                        wrote on last edited by
                        #21

                        Brit posted something where he used 1/infinity but you can't do that. Infinity is a concept, not a number. I thought I heard once that "not all infinities are the same". ------------------------------------------ "Isn't it funny how people say they'll never grow up to be their parents, then one day they look in the mirror and they're moving aircraft carriers into the Gulf region?" - The Onion

                        T 1 Reply Last reply
                        0
                        • B Brit

                          Brit posted something where he used 1/infinity but you can't do that. Infinity is a concept, not a number. I thought I heard once that "not all infinities are the same". ------------------------------------------ "Isn't it funny how people say they'll never grow up to be their parents, then one day they look in the mirror and they're moving aircraft carriers into the Gulf region?" - The Onion

                          T Offline
                          T Offline
                          Taka Muraoka
                          wrote on last edited by
                          #22

                          Yep. For example, say A is the set of all positive, non-zero integers. This is a set of infinite size, of course. Let B be the set of all non-zero integers, positive and negative which is also of infinite size. But for every element in A, there are 2 in B e.g. the number 10 in A corresponds to +10 and -10 in B. So B is twice as big as A. It's a long time since I did any of this but I think to be of "infinite" size means to be uncountable but you can still set up mappings between uncountable sets like the one above and compare their sizes.


                          he he he. I like it in the kitchen! - Marc Clifton (on taking the heat when being flamed) Awasu v0.4a[^]: A free RSS reader with support for Code Project.

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