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Boolean Algebra: Minimum Sum-Of-Products Expression

  1. Sep 13, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the minimum Sum-Of-Product Expression for:
    f = ab'c' + abd + ab'cd'

    3. The attempt at a solution

    By introducing the missing variable in term 1 and term 2 I can get an expression that has all the variables: a, b, c, and d.

    I do so by:

    f = ab'c'd + ab'c'd' + abcd + abc'd + ab'cd'

    I can combine terms like so: (1 & 2),( 2 & 5), (3 & 4) I get:

    f = ab'c' + ab'd' + abd

    This hardly seems minimized from the original expression. Thanks for any help.
     
    Last edited: Sep 13, 2009
  2. jcsd
  3. Sep 13, 2009 #2
    What you've stated is one of two equivalent minsum forms of that Boolean expression. There are several methods for arriving at these (consensus, Karaugh maps, Quine-McCluskey). I'd examine them for more info.

    The original expression has a summand complexity (SC) of 3 and a literal complexity (LC) of 10. The minsum has an SC of 3 and an LC of 9 (as does the other). It isn't much simpler but it as simple as one can get.

    --Elucidus
     
  4. Sep 13, 2009 #3
    Thanks, when you're learning about these concepts it is nice to have confirmation that you are doing things right. Normally it class we get the function down a term or two...or even to one term. So, when I got this down to three terms, with three variables in each term, it didn't really seem minimized. Thanks again!
     
  5. Jul 29, 2010 #4
    Karnaugh product of sums answer:

    a(b+d)(b+c'+d')
     
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