Digital Self Doubt

Question

For this question https://gateoverflow.in/2116/gate2011-14

I have drawn my k-map as follows:

How my approach is wrong?

Comments

I think my minterms are correct. I have considered P as MSB ..

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Then explain why Q' is with P in one of the minterm.

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I got it. Thanks :)

Answer 1

In your Kmap, The minterms for Quad are not written correctly it must be only P. Because you have to write only the bit which is constant in your quad R is changing and Q is also changing but P is constant(1) so write P only. Then you will get P+R'Q'. (FYI in Kmap Both a Pair and Quad cannot have same number of minterms because in quad we will be grouping more terms compared to a pair so it will have less terms.)