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+10 votes
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What values of $A, B, C$ and $D$ satisfy the following simultaneous Boolean equations?

$\overline{A} + AB =0, AB=AC, AB+A\overline{C}+CD=\overline{C}D$

  1. $A=1, B=0, C=0, D=1$

  2. $A=1, B=1, C=0, D=0$

  3. $A=1, B=0, C=1, D=1$

  4. $A=1, B=0, C=0, D=0$

asked in Digital Logic by Veteran (59.6k points)
edited by | 676 views
0
AB+AC'+CD=C'D how we get this part can uh please explain !

3 Answers

+2 votes
Best answer
$A'+AB=0  \implies A'+B=0$

$\therefore A'=0$ and $B=0$

$A=1$

$AB=AC \implies B=C\implies  C=0$

$AB+AC'+CD=C'D$

$\implies 0+1+0=D$

$\implies D=1$
answered by Active (3.1k points)
edited by
0

$AB=AC  \rightarrow  B=C $

Cancellation Law doesn't hold good for boolean algebra.
It holds only when -
$(AB=AC) \ \wedge (A=1)  \rightarrow  B=C $  \\doesn't hold when $A=0.$
and
$(A+B=A+C) \ \wedge (A=0)  \rightarrow  B=C $  \\doesn't hold when $A=1.$

+15 votes
Answer is A.

For verification, just put up the values and check for AND, OR operations and their outputs.
answered by Boss (19.7k points)
+2 votes

"Options make this question pretty straight forward what we need to do just put the options and see which one satisfy the given condition

What if the same question is given in " Numeric" value where we have to find the value of Boolean variable A, B, C, D or asking to find the value in decimal where A(MsB) & D(Lsb) which make bit "tricky"

answered by Loyal (8.1k points)


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