1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Binary multiplication help

  1. Mar 12, 2013 #1
    How do you multiply 111x111. Every exemple i ve found on internet is 101x100, 110x101 and it doesnt answer to my question :|.
    Code (Text):

             111x
             111=
             111+
            111+
           111
           ----
    Every exemple ive found is like :))
      110+
      101
       
    Which is obviously easy...
     
    The problem i have is the summing of 111+111+111, when i get 1+1+1=??? I cant understand how this works in binary :|.
     
  2. jcsd
  3. Mar 12, 2013 #2

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    If you have 9+9+9 in decimal, how does that work?
     
  4. Mar 12, 2013 #3
    i keep the first digit and i add it with the next digits.
    But if i have to sum 1+1+1 in the sum coulm This is (1+1+1+1)=(10+1+1)=100, what i do here, i keep the last digit and i add 10 to the next sum, this is what i dont understand.
     
  5. Mar 12, 2013 #4

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    It's probably easier to see what to do if you add two binary numbers at a time.

    If you have (binary) 111 + 111, then, starting from the rightmost column,

    1+1 = 10, write down 0, carry 1 back to the next column to the left
    1+1+1 = 11, write down 1,carry 1 back to the next column to the left
    1+1+1 = 11, the sum becomes

    11 1 0 is the final result

    check, 7+7 = 14 (decimal)
     
  6. Mar 12, 2013 #5

    Mark44

    Staff: Mentor

    To back up a bit from what SteamKing said, there are four addition facts that come into play.
    1. 0 + 0 = 0
    2. 0 + 1 = 1
    3. 1 + 0 = 1
    4. 1 + 1 = 10
    The only one of these that deserves discussion is the last: 1 + 1 = 0, and you carry 1 to the next higher place.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Binary multiplication help
  1. Binary Relations (Replies: 25)

  2. Binary addition (Replies: 7)

  3. Binary to decimal. (Replies: 4)

Loading...