ISRO2016-10

Question

Consider the following gate network

Which one of the following gates is redundant?

• A. Gate No. $1$
• B. Gate No. $2$
• C. Gate No. $3$
• D. Gate No. $4$

Comments

So, this question's incorrect?

Answer 1

   

                         (1)                                       (2)

o/p=w' + w'z + z'xy                                      O/p = w' +z'xy 

=w' (1+z) + z'xy

=w' +z'xy 

Both (1) and (2) giving the same output.

Hence,Option(B)Gate No. 2

Comments

Solution is very simple.

Gate 1 contact I/p as 'w' and if we remove gate 1 we cannot get 'w' in our output.

Gate 3 contains z,x,y as I/p of we remove then x, y input will be lost .

Gate 4 is the final gate where we are getting out of all the gates so we cannot remove .

Gate 2 contains two I/p w' and z ,if we remove both I/p then nothing will change bec gate 1 and gate 5 contains  w' and z . So it's clear gate 2 is redundant.

I hope u got it.

It takes hardly 15 secons to solve this question.

Answer 2

The above circuit produces the expression w'+w'z+z'xy  which is simplified to w'(1+z) +z'xy =w'+z'xy so the gate no 2 which produces w'z is redundant as it has been eliminated in final result  

hence ans is B

Comments

@Sanjay Sharma

Sir is there any quick method to solve this?

This was a pretty easy que but for the tricky questions, quick method could be more handly.