# Math Help - binary division discrepancy

1. ## 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.

2. ## Re: binary division discrepancy

It is wrong. In the second part of the division they take 1101 away from 1011 incorrectly.

3. ## 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.

4. ## 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

5. ## 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.

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

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