Tag: proofs in mathematics

Questions Related to proofs in mathematics

Consider the following statements 
$p$:you want to success
$q$:you will find way,
then the negation of $\sim (p\vee q)$ is

  1. you want of success and you find a way

  2. you want of success and you do not find a way

  3. if you do not want to succeed then you will find a way

  4. if you want of success then you cannot find a way


Correct Option: A

Which of the following statements is a tautology

  1. $\left( { \sim p \vee q} \right) - \left( {p \vee \sim q} \right)$

  2. $\left( { \sim p \vee \sim q} \right) \to p \vee q$

  3. $\left( {p \vee \sim q} \right) \wedge \left( {p \vee q} \right)$

  4. $\left( { \sim p \vee \sim q} \right) \vee \left( {p \vee q} \right)$


Correct Option: C

Which of the following is a logical statement?

  1. Open the door

  2. What an intelligent student!

  3. Are you going to Delhi

  4. All prime numbers are odd numbers


Correct Option: D
Explanation:

The above $3$ statements are basic statements.

But the $4$ statement is a logical statement.
All prime numbers are odd numbers.

The proposition $\left( {p \wedge q} \right) \Rightarrow p$ is 

  1. neither tautology nor contradiction

  2. A tautology

  3. A contradiction

  4. Cannot be determined


Correct Option: B

The statement $p \to (q \to p)$ is equivalent to 

  1. $p \to q$

  2. $p \to (q \vee p)$

  3. $p \to (q \to p)$

  4. $p \to (q \wedge p)$


Correct Option: B

Which of the following is correct?

  1. $(~p \vee ~q) \equiv (p \wedge q)$

  2. $(p \rightarrow q) \equiv (~q \rightarrow ~p)$

  3. $~(p \rightarrow ~q) \equiv (p \wedge ~q)$

  4. $~(p \leftrightarrow q) \equiv (p \rightarrow q) \wedge (q \rightarrow p)$


Correct Option: D
Explanation:


$~(p \leftrightarrow q) \equiv (p \rightarrow q) \wedge (q \rightarrow p)$ is true, we show it by truth table using boolean expression.

1.$p\rightarrow q$=min(1,1+q-p)
2.$p\wedge q$=min(p,q)
3.$p\leftrightarrow q$=1-|p-q|

Now we draw or make truth table using these operations
L.H.S  

 p  q $p\leftrightarrow q$ 
 1


R.H.S 

p $p\rightarrow q$  $q\rightarrow p$   $(p \rightarrow q) \wedge (q \rightarrow p)$
1  1  1  1
1  0

L.H.S =R.H.S

$~(p \leftrightarrow q) \equiv (p \rightarrow q) \wedge (q \rightarrow p)$

$(p \wedge q) \vee  \sim p$ is equivalent to 

  1. $\sim p \wedge q$

  2. $\sim p \vee q$

  3. $p \wedge q$

  4. $p \vee q$


Correct Option: A

In a certain code language, $'543'$ means 'give my water'; $'247'$ means 'water is life' and $'632'$ means 'enjoy my life'. Which of the following stands for 'enjoy' in that language?

  1. $7$

  2. $6$

  3. $2$

  4. $5$


Correct Option: A

$\sim (p \wedge q)\Rightarrow (\sim p)\vee (\sim p \vee q)$ is equal to

  1. $\sim p \vee q$

  2. $\sim p \wedge q$

  3. $p\vee \sim q$

  4. $p\wedge \sim q$


Correct Option: A

The equivalent of $(p \rightarrow \sim p) \vee (\sim p \rightarrow p)$ is 

  1. $p \vee \sim p$

  2. $T \rightarrow F$

  3. $T \leftrightarrow F$

  4. $p \wedge \sim p$


Correct Option: A