The Boolean expression of the output f of the multiplexer shown below is:
[4:1 MUX with select lines P (MSB) and Q (LSB), data inputs: I0=0, I1=1, I2=R, I3=R']
A. P'Q + P(Q XOR R)
B. P + Q XOR R
C. P'Q XOR R
D. P' + Q*R
GATE 2010 · Digital Logic · Circuit Output · easy
Answer: f = P'Q + P(Q XOR R), which is option A.
Expand the MUX output using the standard formula: f = P'Q'*0 + P'Q*1 + PQ'*R + PQ*R'
= 0 + P'Q + PQ'R + PQR'
Simplify by factoring P: Group the last two terms: PQ'R + PQR' = P*(Q'R + QR') = P*(Q XOR R)
So: f = P'Q + P(Q XOR R)