Posers and Puzzles

Posers and Puzzles

  1. Standard membersmw6869
    Granny
    Parts Unknown
    Joined
    19 Jan '07
    Moves
    73101
    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. Joined
    02 Jul '07
    Moves
    2416
    06 Sep '07 03:306 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. Joined
    01 Sep '07
    Moves
    5679
    06 Sep '07 11:47
    Great
  4. Joined
    31 May '07
    Moves
    696
    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 memberagryson
    AGW Hitman
    http://xkcd.com/386/
    Joined
    23 Feb '07
    Moves
    7113
    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. Joined
    12 Mar '03
    Moves
    37893
    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 memberagryson
    AGW Hitman
    http://xkcd.com/386/
    Joined
    23 Feb '07
    Moves
    7113
    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. Under Cover
    Joined
    25 Feb '04
    Moves
    28912
    07 Sep '07 08:19
    How about 10+10=100
  9. Joined
    12 Mar '03
    Moves
    37893
    07 Sep '07 09:04
    binary

    but 10 x 10 = 100 is less clear 😵
  10. Joined
    31 May '07
    Moves
    696
    07 Sep '07 16:06
    6+5=3 anyone?
  11. Standard memberwolfgang59
    Mr. Wolf
    at home
    Joined
    09 Jun '07
    Moves
    46092
    07 Sep '07 21:17
    mod 8
  12. Joined
    29 Jan '07
    Moves
    3612
    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. Joined
    29 Jan '07
    Moves
    3612
    09 Sep '07 13:321 edit
    how about 8+8=15...

    anyone who's a musician should get that
  14. Standard memberwolfgang59
    Mr. Wolf
    at home
    Joined
    09 Jun '07
    Moves
    46092
    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. Joined
    29 Jan '07
    Moves
    3612
    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!
Back to Top