Question

Logic gates $X$ and $Y$ have the truth tables shown below:

$X$			$Y$
0	0	0	0	1
1	0	0	1	0
0	1	0
1	1	1

When the output of $X$ is connected to the input of $Y$, the resulting combination is equivalent to a single

• A. NOT gate
• B. OR gate
• C. NAND gate
• D. AND gate

Answer 1

Answer: (C)

The truth table of the resulting logic circuit by connecting $X$ to $Y$ is as follows

$P$	$Q$	$R$	$R$
0	0	0	1
1	0	0	1
0	1	0	1
1	1	1	0

Hence, from the truth table, the combination is equivalent to a single NAND gate.
(OR $X$ is an AND gate and $Y$ is a NOT gate, thus the combination is NOT AND gate, i.e., a NAND gate)