Question

If the output $Y$ of the following circuit is $1$, the inputs $ABC$ must be :

• A. $010$
• B. $100$
• C. $101$
• D. $110$

Answer 1

Answer: (C)

$101$

From left, the first gate is OR gate and the output of OR gate is $Y_1=A+B$ and the second gate is AND gate.

The output of AND gate is $Y=Y_1.C=(A+B).C$

For $010,Y=(0+1).0=0$;

For $100,Y=(1+0).0=0$;

For $101,Y=(1+0).1=1$ and

For $110,Y=(1+1).0=1.0=0$