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Math Help - binary division discrepancy

  1. #1
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    binary division discrepancy

    Hello, I am trying to understand the following modulo 2 long division.
    I understand that 1101 goes into 1111, so you write a 1 on the top.
    The next stage after 'XOR'ing is to bring down the 1.
    Now, 1101 does not go into 101, so you write a 0 at the top. So far so so good.
    Now you bring down another 1 and 1101 still does not go into 1011, so how come they wrote a 1 in the third position at the top ? Shouldn't that be a zero ?

    If someone could please explain where I am going wrong, I would most grateful.
    Attached Thumbnails Attached Thumbnails binary division discrepancy-difv.jpg  
    Last edited by fran1942; March 20th 2013 at 01:18 AM.
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  2. #2
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    Re: binary division discrepancy

    It is wrong. In the second part of the division they take 1101 away from 1011 incorrectly.
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  3. #3
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    Re: binary division discrepancy

    sorry, I have explained myself more clearly in the edited first post.
    Still looking for an answer if anyone can help.
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    Re: binary division discrepancy

    Ok I thought you just wanted confirmation that it was wrong.

    so how come they wrote a 1 in the third position at the top ? Shouldn't that be a zero ?
    Yes they made a big mistake there.

    It should look like this
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  5. #5
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    Re: binary division discrepancy



    \text{Hello, fran1942!}


    \text{The problem is: }\:2026 \div 13 \:=\:155, r11

    Code:
    
                          1 0 0 1 1 0 1 1
                  -----------------------
          1 1 0 1 | 1 1 1 1 1 1 0 1 0 1 0
                    1 1 0 1
                    -------
                        1 0 1 1 0
                          1 1 0 1
                        ---------
                          1 0 0 1 1
                            1 1 0 1
                            --------
                              1 1 0 0 1
                                1 1 0 1
                              ---------
                                1 1 0 0 0
                                  1 1 0 1
                                ---------
                                  1 0 1 1
    I suspect a typo in the problem.


    \text{If the dividend were }11,\!111,\!101,\!{\color{red}10}\;\!0_2

    . . \text{the problem would be: }\:2028 \div 13 \:=\:156
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