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One of the Oldest Math Tricks

January 17th, 2010 by Steven Pomeroy | Filed under Math Tricks.




Many of you may have seen this one before – it is very old (I first saw this in grade school, which makes this example of math tricks ancient!).

Yes, it is the infamous 2=1 “proof”.  Here I present it to you as a graphic an also as a video set to Beethoven’s 5th (yea – it was raining yesterday so I had a lot of time on my hands!).

First, here is the graphic of the proof:

And now for the video proof:

So that is the proof.  Can you spot where the error is?

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10 Responses to “One of the Oldest Math Tricks”

  1. Marco | 19/01/10

    By the first line: A=B => A-B=0


    (A+B)(A-B) = A(A-B)

    You can’t divide by (A-B), you can’t divide by 0!

  2. mike | 9/02/10

    as said a-b never cancelled bcoz a-b=0 and 0 never cancels other 0

  3. Ryan | 10/02/10

    don’t call it a proof. it’s not a proof.

  4. masaru shinoda | 9/03/10

    ahahahahaha.. it’s a nice trick.. ^_^v

    if A=B

    so, A-B = 0 right.?

    therefore: => (A+B)(A-B) = A(A-B)

    => (A+B)(A-B) = A(A-B)
    ——– —-
    (A-B) (A-B)

    => Let us A=2 and B=1; therefore; (A-B) is (2-1)
    => so the A-B = 0

    => the solution must be undefine…

    …………………………..♣cUtEmAntsAnG♣………………

  5. nicole | 2/10/10

    haha thats ridiculous .. 2=1, but u see its true

  6. Stanley | 22/12/12

    how did u get the third line?

  7. Math Tricks | 23/12/12

    Stanley, given that A=B, you can write this line as it is, and then continue with the rest of the argument.

  8. ilyas | 3/03/14

    Realy amazing

  9. Om division och multiplikation med variabler (som x) i ekvationer. | mattekliniken | 9/06/14

    […] mattetrick 1 […]

  10. Mehehe | 10/11/14

    Yeah, cause its like saying 1000 . 0 = 5 . 0
    Does that mean, that 1000 = 5? No…..

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