ACE Test Series

Question

Can we verify such examples using truth tables?

Using truth table answer comes as the contingency.(Since for pqr==011 it comes 0 and for all other combinations answer is 1).

But the answer given is Option(A).

I am so confused.

Ans also how to verify if given expression is satisfiable or valid or both or none.

Comments

ankit ..

to solve such problem just try to eliminate option....

for option A....

expression could be false only if 

p F and left side combination is true( r true q true )....and it is possible therefor not tautology....

for option C...

if p is false then it would be true....

..means not a tautology nor cotradiction means contigency....

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Questions like these can be solved by using truth tables but we need to be smart here.

Just randomly put T for all variables and check the truth value.

Next,put F for all values and check the truth value.Depending on the question we can easily figure that it is tautology or contradiction or contigency.