4 replies to this topic

[ZipOnTrousers]

Hi, I'm working through some Multi-digit binary multiplications and I've come to a halt. I apparently don't know how to carry 1s anymore... I'll show you what I mean. This is the sum with the correct answer: (note the dots are jsut to ensure everything is spaced correctly, they can be ignored)

............1101101
*............100110
..........1101101
........1101101
...1101101
.1000000101110

However my problem arises in that column where you are adding three 1s together, and there is also a carried 1. So that column basically = 1 + 1 + 1 + 1. I thought this would be 1 carry 1, but I realised thats when you're adding three 1s. Since the solution has a 0 in the result of this column, does that mean that 1 + 1 + 1 + 1 is 1 + 1 = 0 carry 1 plus 1 + 1 which is ANOTHER 0 carry another 1? Do you just carry a single 1 across into the next column?

I suppose my question can be summarised as: In binary, when you are adding 4 or more ones together do you carry across more than a single 1?

Sorry if thats confused anyone >_>

[WingedPanther]

     1101101

      100110

------------

    1101101

   1101101

 1101101

------------

           0

          1

         1

        1

      11

      1

    10

   11

   1

  1

 1

------------

           0

          1

         1

        1

       1

     10

     0

   10

  10

  1

 1

------------

           0

          1

         1

        1

       1

      0

     1

    0

   1

 10

 1

------------

           0

          1

         1

        1

       1

      0

     1

    0

   1

  0

10

------------

100101011110

[ZipOnTrousers]

Sorry Winged, would you be able to explain that post lol? Struggling to understand just the 0s and 1s

[WingedPanther]

Basically, I'm adding each each column and listing the results on separate rows. I then repeat the process to handle the carrying.

[John]

When I do binary multiplication, I like to do the addition every step rather than waiting until the end. However, when you add 1+1+1+1 you get (4) 100, so I believe you put down a zero (the least significant bit) and carry the 10.