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Homework Help: Weird logic-design exam questions

  1. Mar 27, 2007 #1
    1. The problem statement, all variables and given/known data

    Here are three problems from an exam and i'm not sure i understand the wording... almost like we're supposed to get these wrong.

    4. The Boolean expression of the OR between minterm 6 and minterm 7 using variables ABC (A being the MSB and C being the LSB) is
    {(A)} AB
    (B) AC
    (C) BC
    (D) A+B
    (E) A+C

    6. The Boolean expression of the AND between minterm 6 and minterm 7 using variables ABC (A being the MSB and C being the LSB) is
    {(A)} 0
    (B) 1
    (C) A
    (D) A'
    (E) B

    15. The Boolean expression of the OR between maxterm 6 and maxterm 7 using variables ABC (A being the MSB and C being the LSB) is
    (A) 0
    {(B)} 1
    (C) A
    (D) A'
    (E) B

    Correct answers are marked.

    3. The attempt at a solution

    I did a k map and got AB as the sop for minterm 6 and minterm 7, and (A' + B') for the pos between maxterm 6 and 7, and AB looks like the answer for 4.

    My problem is i have no idea what the questions are asking for,...well that and the TA didn't respond to my email :tongue:
     
  2. jcsd
  3. Mar 29, 2007 #2
    Well i checked with some software and my results for pos and sop are correct...

    Owell, got my energy drinks so i'm gonna go study lol
     
  4. Mar 29, 2007 #3
    Ok i think i found a pattern that works atleast with these problems... correct me if i'm wrong :rofl:


    For the Boolean expression of the OR between minterm 6 and minterm 7
    They asked for the OR at minterms, do standard sop with k map = answer = AB

    For the Boolean expression of the AND between maxterms 6 and maxterm 7
    They asked for the AND at minterms, do standard pos with k map = answer = A'+B'

    For the Boolean expression of the AND between minterm 6 and minterm 7
    They asked for the AND at minterms, ...so convert the problem to equilivant maxterm form... which is 0's everywhere except at 6 and 7. I got a pos of (A+B)...and you see the "+"... that means, no their is not AND between them... so 0

    For the Boolean expression of the OR between maxterm 6 and maxterm 7
    They asked for the OR between maxterms...convert the problem to equilivant minterm form... which is 1's everywhere except 6 and 7. i got a sop of A'+B'...and you see the "+"...that means yes their is a OR between them, so 1

    So yea that's the best guess i can ever do and it should work atleast some of the time :P

    p.s. i had my exam and those questions weren't in the second exam... my teacher gave me a trashy homework grade though...like 2/21 despite the DAYS! i spent to make sure the hw was very correct, maybe he just checks the last one lol where i was a little iffy :P.... DON"T CARE... i'll pass the exams and say good bye (nah i'd say something i probably can't say in these forums) to the evil teacher :P
     
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