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Propositional Logic: Tautologies and Contradictions

Description: Propositional Logic: Tautologies and Contradictions
Number of Questions: 15
Created by:
Tags: propositional logic tautologies contradictions
Attempted 0/15 Correct 0 Score 0

Which of the following is a tautology?

  1. ~(p ∨ q)

  2. (p ∧ q) → p

  3. p → (p ∨ q)

  4. ~(p → q) → p


Correct Option: C
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "p → (p ∨ q)" is always true, because if "p" is true, then "p ∨ q" is also true, and if "p" is false, then "p → (p ∨ q)" is also true.

Which of the following is a contradiction?

  1. (p ∧ q) → p

  2. ~(p ∨ q)

  3. p → (p ∨ q)

  4. ~(p → q) → p


Correct Option: B
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p ∨ q)" is always false, because if "p" is true or "q" is true, then "p ∨ q" is true, and "~(p ∨ q)" is false.

Which of the following is a tautology?

  1. ~(p ∧ q) → (~p ∨ ~q)

  2. (p ∨ q) → (~p → q)

  3. (p → q) → (~q → ~p)

  4. ~(p → q) → (p ∧ ~q)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p ∧ q) → (~p ∨ ~q)" is always true, because if "p ∧ q" is false, then "~p ∨ ~q" is true, and if "p ∧ q" is true, then "~(p ∧ q)" is false.

Which of the following is a contradiction?

  1. (p ∨ q) → (~p → q)

  2. (p → q) → (~q → ~p)

  3. ~(p → q) → (p ∧ ~q)

  4. ~(p ∧ q) → (~p ∨ ~q)


Correct Option: C
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p → q) → (p ∧ ~q)" is always false, because if "p → q" is false, then "p ∧ ~q" is true, and if "p → q" is true, then "~(p → q)" is false.

Which of the following is a tautology?

  1. (p ∨ q) → (q ∨ p)

  2. (p ∧ q) → (q ∧ p)

  3. ~(p ∨ q) → (~p ∧ ~q)

  4. ~(p ∧ q) → (~p ∨ ~q)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "(p ∨ q) → (q ∨ p)" is always true, because if "p ∨ q" is true, then "q ∨ p" is also true, and if "p ∨ q" is false, then "(p ∨ q) → (q ∨ p)" is also true.

Which of the following is a contradiction?

  1. (p ∧ q) → (q ∧ p)

  2. ~(p ∨ q) → (~p ∧ ~q)

  3. ~(p ∧ q) → (~p ∨ ~q)

  4. (p ∨ q) → (q ∨ p)


Correct Option: C
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p ∧ q) → (~p ∨ ~q)" is always false, because if "p ∧ q" is false, then "~p ∨ ~q" is true, and if "p ∧ q" is true, then "~(p ∧ q)" is false.

Which of the following is a tautology?

  1. ~(p → q) → (p ∧ ~q)

  2. (p ∨ q) → (~p → q)

  3. (p → q) → (~q → ~p)

  4. ~(p ∧ q) → (p → ~q)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p → q) → (p ∧ ~q)" is always true, because if "p → q" is false, then "p ∧ ~q" is true, and if "p → q" is true, then "~(p → q)" is false.

Which of the following is a contradiction?

  1. (p ∨ q) → (~p → q)

  2. (p → q) → (~q → ~p)

  3. ~(p ∧ q) → (p → ~q)

  4. ~(p → q) → (p ∧ ~q)


Correct Option: C
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "~(p ∧ q) → (p → ~q)" is always false, because if "p ∧ q" is false, then "p → ~q" is true, and if "p ∧ q" is true, then "~(p ∧ q)" is false.

Which of the following is a tautology?

  1. (p → q) → ((q → r) → (p → r))

  2. ((p → q) ∧ (q → r)) → (p → r)

  3. ((p → q) ∨ (q → r)) → (p → r)

  4. ~(p → q) → (p ∧ ~q)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "(p → q) → ((q → r) → (p → r))" is always true, because if "p → q" is true, then "(q → r) → (p → r)" is also true, and if "p → q" is false, then "(p → q) → ((q → r) → (p → r))" is also true.

Which of the following is a contradiction?

  1. ((p → q) ∧ (q → r)) → (p → r)

  2. ((p → q) ∨ (q → r)) → (p → r)

  3. ~(p → q) → (p ∧ ~q)

  4. (p → q) → ((q → r) → (p → r))


Correct Option: B
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p → q) ∨ (q → r)) → (p → r)" is always false, because if "p → q" is true and "q → r" is false, then "p → r" is false, and "((p → q) ∨ (q → r)) → (p → r)" is also false.

Which of the following is a tautology?

  1. ((p ∨ q) ∧ (p → r)) → (q → r)

  2. ((p ∧ q) ∨ (p → r)) → (q → r)

  3. ((p → q) ∧ (q → r)) → (p → r)

  4. ((p ∨ q) ∨ (p → r)) → (q → r)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p ∨ q) ∧ (p → r)) → (q → r)" is always true, because if "p ∨ q" is true and "p → r" is true, then "q → r" is also true, and if "p ∨ q" is false or "p → r" is false, then "((p ∨ q) ∧ (p → r)) → (q → r)" is also true.

Which of the following is a contradiction?

  1. ((p ∧ q) ∨ (p → r)) → (q → r)

  2. ((p → q) ∧ (q → r)) → (p → r)

  3. ((p ∨ q) ∨ (p → r)) → (q → r)

  4. ((p ∨ q) ∧ (p → r)) → (q → r)


Correct Option: A
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p ∧ q) ∨ (p → r)) → (q → r)" is always false, because if "p ∧ q" is true and "p → r" is false, then "q → r" is false, and "((p ∧ q) ∨ (p → r)) → (q → r)" is also false.

Which of the following is a tautology?

  1. ((p → q) ∧ (q → r)) → (p → r)

  2. ((p ∨ q) ∧ (p → r)) → (q → r)

  3. ((p ∧ q) ∨ (p → r)) → (q → r)

  4. ((p → q) ∨ (q → r)) → (p → r)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p → q) ∧ (q → r)) → (p → r)" is always true, because if "p → q" is true and "q → r" is true, then "p → r" is also true, and if "p → q" is false or "q → r" is false, then "((p → q) ∧ (q → r)) → (p → r)" is also true.

Which of the following is a contradiction?

  1. ((p ∨ q) ∧ (p → r)) → (q → r)

  2. ((p → q) ∨ (q → r)) → (p → r)

  3. ((p ∧ q) ∨ (p → r)) → (q → r)

  4. ((p → q) ∧ (q → r)) → (p → r)


Correct Option:
Explanation:

A contradiction is a propositional formula that is always false, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p ∨ q) ∨ (p → r)) → (q → r)" is always false, because if "p ∨ q" is true and "p → r" is false, then "q → r" is false, and "((p ∨ q) ∨ (p → r)) → (q → r)" is also false.

Which of the following is a tautology?

  1. ((p → q) ∧ (q → r)) → (p → r)

  2. ((p ∨ q) ∧ (p → r)) → (q → r)

  3. ((p ∧ q) ∨ (p → r)) → (q → r)

  4. ((p → q) ∨ (q → r)) → (p → r)


Correct Option: A
Explanation:

A tautology is a propositional formula that is always true, regardless of the truth values of its constituent propositions. In this case, the propositional formula "((p → q) ∧ (q → r)) → (p → r)" is always true, because if "p → q" is true and "q → r" is true, then "p → r" is also true, and if "p → q" is false or "q → r" is false, then "((p → q) ∧ (q → r)) → (p → r)" is also true.

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