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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

450.0. "If 5/2 = 3 then 20/3 = ?" by KEEPER::KOSTAS () Fri Mar 07 1986 23:44

    Hello,
    
         here is the problem:
    
         If 5/2 = 3 then 20/3 = ?
    
    Enjoy.
    
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450.1Oh, goodie, an easy oneCLT::YARBROUGHMon Mar 10 1986 12:243
    Anything you choose. The statement "If false then A" is satisfied
    by any statement A. Since 5/2=3 is false for any default notation,
    A can be anything.
450.2an answerAVANTI::OSMANEric, Maynard Ma. USA, DTN 223-6664Mon Mar 10 1986 13:5530
    Well, let's see.
    
    	5/2 = 3.
    
    So,
    
    	5/3 = 2.   (by some pattern I remember from grade VI !)
    
    So,
    
    	4*5/3 = 4*2.  (do same thing to both sides)
    
    Hence,
    
        20/3 = 8.
    
    Is this what you're looking for ?
    
    I'm not happy about it, though, by what Mr. Yarborough pointed out.
    However, it sort of assumes "suppose 5/2 = 3 and the rest of the
    universe is as we know it.  What would 20/3 be ?"  Such a qualification
    might allow me to perform the steps I used, namely the grade VI
    pattern and "multiplying both sides by the same thing", not to mention
    the assumption that "*" produces the answers I gave.
    
    But even that qualification doesn't get us out of trouble, since
    if the rest of the universe is as we know it, we might as well just
    skip all my steps and say 20/3 is what it always was.
    
    /Eric
450.3Eric has the right idea.KEEPER::KOSTASTue Mar 11 1986 00:5721
    Eric is correct. The traditional answer is 8. You must make
    proportional errors. Here is a real example: 1/2 of 5 Canadian
    quards is 12 1/2 cups, which is very close to 3 of our quards.
    
    If we introduce a factor m on the left hand side of the equation
    and a factor n on the right side then we have:
    
    (5/2)*m = 3*n  
    
    and seek for the proper number  x,
    
    (20/3)*m = x*n
    
    and (20/3) / (5/2) = x/3
    
       =>  x = 8
    
    
    
    Kostas G.
    
450.4Oh, my, I may have found a pigeonMETOO::YARBROUGHTue Mar 11 1986 11:574
    Nonsense. If 5/2=3, then (5/2)*2=3*2=6, so 5=6, so 0=1, so 0=100.
    
    I will therefore accept your answer as correct only if you will
    give me $100 each time I offer you $0.00. That's fair, isn't it?
450.5The check is in the mail.KEEPER::KOSTASWed Mar 12 1986 00:1717
    More can be said upon this subject. It is one of the surprising
    theorems, proved in the new symbolic logic, that from a false
    assumption, any conclusion whatever, true or false, can be drawn
    by legitimate reasoning. 
    
    The mathematician, Hardy, once made this statement at the Commons 
    Table at his university whereupon an incredulous Scotch Don cried 
    out: 
         "Nonsense! Four is six: prove I am the Pope." 
    
    Hardy then made the reply: 
    
         "Lets us see: 4 = 6, divide by 2, then 2 = 3, subtract 1 
         from each side, then 1 is 2. Now it is well known that you 
         and the Pope are 2, and therefore you and the Pope are One!"
                                           
    
450.6SeventeenCLT::GILBERTJuggler of NoterdomWed Mar 12 1986 03:004
If 5/2 = 3, then 20/3 = 17.  The simplest explanation of the premiss
is that '/' really denotes subtraction.

(BTW .5 is EXCELLENT!  I'd never heard this before, and am still smiling)
450.7Seven!EUCLID::MCKINLEYWed Mar 12 1986 12:325
    Integer arithmetic!
    5 / 2  = 2.5 = 3
    20 / 3 = 6.7 = 7
    
    :-)
450.8many answers possibleEAGLE1::BESTR D Best, Systems architecture, I/OThu Apr 30 1987 18:3411
  I got 8, but also wasn't happy.  My problem is that given

	5/2 = 3

I am immediately put on notice that one or more of the symbols 5, 2, /,
3 has some meaning other than the conventional.  However, this doesn't
seem sufficient to tell me which symbols have a redefined meaning, so
I'm reduced to guessing.  Without knowing the redefinition, I can't
unambiguously interpret '20' in the second part.

  Interesting.