Weird Binary Conversion Questions

Discussion in 'Cisco' started by tman, Mar 3, 2008.

  1. tman

    tman Guest

    I have been studying for the CCNA test. I have been using the
    Trainsignal DVD which is very thorough. But when I tried some
    parctice tests at the Cisco website I got a couple of binary
    conversion questions that I did not understand. Can someone explain
    the meaning of these two questions.

    18. The decimal number 452 converted into a binary number, using
    successive division by 2, is _____.

    111000100
    110000100
    111001100
    101000100




    20. The binary number 11101000111 converted into a decimal number,
    using powers of 2, is _____.

    1183
    1873
    1638
    1863

    Thanks
     
    tman, Mar 3, 2008
    #1
    1. Advertisements


  2. Its asking you to do a couple binary conversions. Since IP addresses
    and especially netmasks are numbers that can be expressed as binary
    numbers for ease of use to illustrate what is really going on, its is
    useful to know how to express decimal numbers as binary and back again.


    Its asking you to convert 452 to binary. There's generally two
    different ways you can do it by hand. Here's a website that outlines it.

    http://www.allaboutcircuits.com/vol_4/chpt_1/6.html

    Its asking you to convert 11101000111 to decimal. The same website
    probably has some page about this explicitly, but this is simpler to
    illustrate in a posting..

    1 * 2^0
    1 * 2^1
    1 * 2^2
    0 * 2^3
    0 * 2^4
    0 * 2^5
    1 * 2^6
    0 * 2^7
    1 * 2^8
    1 * 2^9
    1 * 2^10 +
    ===========

    Multiple it out, add it up, and it equals what?

    Again, they are just asking you to do the binary to decimal and back
    again by hand rather than by calculator (if yours supports it).
     
    Doug McIntyre, Mar 3, 2008
    #2
    1. Advertisements

  3. tman

    tman Guest

    Thanks Doug. i understand it now. My problem earlier was I did not
    understand the language e.g., powers of 2 and successive division by
    2. I had learned the "trial-and-fit" method.

    Thanks again for your help.
     
    tman, Mar 4, 2008
    #3
  4. Isn't base conversion still taught in grade school? That's where I
    learned it about 35 years ago.

    But I'll bet most of you thought "I'll never need to use this in real
    life." :)
     
    Barry Margolin, Mar 4, 2008
    #4
  5. tman

    Bod43 Guest

    This is real life???

    Think yourself lucky, the window of opportunity
    is closing:)

    IPV6 will do away with it.

    Of course you need a slightly different conversion
    Hex-Binary but that of course is easy without
    requiring formal methods. I suppose formal methods may
    be needed in the initial learning stages.
     
    Bod43, Mar 4, 2008
    #5
  6. I ran into this question too and could not figure it out but finaly I found a way to get to the right answer. I found it using this method.

    We all know that if we have 8 bits we use :

    128 64 32 16 8 4 2 1

    In this question we do not have 8 bits but we have 11 bits

    (11101000111)

    When you continue counting from bit 128 you will get this.

    1024 512 256 128 64 32 16 8 4 2 1

    Then if we add the bits which are enabled you get :


    1024 512 256 128 64 32 16 8 4 2 1
    1 1 1 0 1 0 0 0 1 1 1

    1024 + 512 + 256 + 64 + 4 + 2 + 1 = 1863










    Op maandag 3 maart 2008 18:58:38 UTC+1 schreef tman het volgende:
     
    wimkuijpers65, Aug 29, 2012
    #6
  7. 1024 512 256 128 64 32 16 8 4 2 1
    1 1 1 0 1 0 0 0 1 1 1






    Op maandag 3 maart 2008 18:58:38 UTC+1 schreef tman het volgende:
     
    wimkuijpers65, Aug 29, 2012
    #7
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.