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Posers and Puzzles

Posers and Puzzles

  1. Standard member smw6869
    Granny
    06 Sep '07 02:01
    Anyone know how to prove this to be true(even though it's not). A math teacher proved it to my math class. Everything made sense and no one could find the falacy.
  2. 06 Sep '07 03:30 / 6 edits
    Originally posted by smw6869
    Anyone know how to prove this to be true(even though it's not). A math teacher proved it to my math class. Everything made sense and no one could find the falacy.
    If there is a general formula involved in the proof, make sure division by zero isn't happening because that isn't allowed. So for example the classic case of the fallacy of 1=2 (which is very similar to yours)
    step 1
    Let a = b
    step 2 Multiply both sides by a:
    aa = ab
    step 3 which is the same as:
    a^2 = ab ( "a squared equals a times b" )
    step 4 Add the quantity ( a^2 - 2ab) to both sides:
    a^2 + (a^2 - 2ab) = ab + (a^2 - 2ab)
    step 5 simplifying both sides we get:
    (a^2 + a^2) - 2ab = a^2 + (ab - 2ab)
    2(a^2) - 2ab = a^2 - ab
    2 (a^2 - ab) = a^2 - ab
    step 6 divide both sides by (a^2 - ab):
    2(a^2 - ab) / (a^2 - ab) = (a^2 - ab) / (a^2 -ab)
    step 7 cancel out like terms in num.&denom:
    2 = 1 !!!

    Two equals one? Impossible! What's the catch? The catch is, our very first assumption is Let a= b, and if that's true then the quantity (a^2 - ab) = (a^2 - a^2) = 0, and we are not allowed to divide by zero which is what we do in our "proof" in step 6. The proof is not allowed. No division by zero.

    I bet this is the trick that is happening in your false proof of 2+2=5.

    (sorry for all the edits, but I had to work out some formatting issues)
  3. 06 Sep '07 11:47
    Great
  4. 06 Sep '07 14:34
    This is generally to do with rounding:
    2.4 rounds to 2
    2.4+2.4=4.8 which rounds to 5.

    If you round everything: 2+2=5
  5. Standard member agryson
    AGW Hitman
    06 Sep '07 19:24
    An alternative to this one I came across is this...

    2+2=10

    This is mathematically true, and breaks no rules, but I've left out one piece of information. What's the information I've left out?
  6. 06 Sep '07 19:40
    Originally posted by agryson
    An alternative to this one I came across is this...

    2+2=10

    This is mathematically true, and breaks no rules, but I've left out one piece of information. What's the information I've left out?
    base 4
  7. Standard member agryson
    AGW Hitman
    06 Sep '07 19:42
    Originally posted by Mephisto2
    base 4
    Got it. Though when i was told it, the dumbass mixed them up and said
    2+2=5... in base four. I slapped him over the back of the head.
  8. 07 Sep '07 08:19
    How about 10+10=100
  9. 07 Sep '07 09:04
    binary

    but 10 x 10 = 100 is less clear
  10. 07 Sep '07 16:06
    6+5=3 anyone?
  11. Standard member wolfgang59
    Infidel
    07 Sep '07 21:17
    mod 8
  12. 09 Sep '07 13:32
    no its not, if it's binary then it would either be 10 + 10 = 4 or 10 = 10 = 256; all depends where the other six zeros are
  13. 09 Sep '07 13:32 / 1 edit
    how about 8+8=15...

    anyone who's a musician should get that
  14. Standard member wolfgang59
    Infidel
    09 Sep '07 13:47
    Originally posted by eatmybishop
    no its not, if it's binary then it would either be 10 + 10 = 4 or 10 = 10 = 256; all depends where the other six zeros are
    In binary there is no '4' or '256'

    10+10=100 is quite correct (ie 2+2=4 in decimal)

    10x10=100 is true in any base.
  15. 12 Sep '07 18:38
    Originally posted by wolfgang59
    In binary there is no '4' or '256'

    10+10=100 is quite correct (ie 2+2=4 in decimal)

    10x10=100 is true in any base.
    no its not, you're wrong...

    i was under the impression is was binary to decimal.. so you're right there, there is no 4 or 256 in binary... however you're still wrong...

    in binary, it would be 10+10=10... you are wrong to say 100, its not, 1 + 1 = 1 or 0 + 1 = 1, 0 + 0 = 0.... there is no additional digit.... mr dumb!