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Propositional Logic: Logical Arguments and Soundness

Description: This quiz evaluates your understanding of propositional logic, logical arguments, and the concept of soundness.
Number of Questions: 15
Created by:
Tags: propositional logic logical arguments soundness
Attempted 0/15 Correct 0 Score 0

Which of the following is a propositional variable?

  1. A

  2. B

  3. C

  4. D


Correct Option: A
Explanation:

A propositional variable is a letter that represents a proposition, which is a statement that is either true or false.

What is the truth value of the proposition "2 + 2 = 5"?

  1. True

  2. False


Correct Option: B
Explanation:

The proposition "2 + 2 = 5" is false because the sum of 2 and 2 is 4, not 5.

Which of the following is a logical connective?

  1. And

  2. Or

  3. Not

  4. If-then


Correct Option: A
Explanation:

A logical connective is a word or symbol that connects two or more propositions to form a compound proposition.

What is the truth value of the compound proposition "(P ∧ Q) ∨ ¬R" if P is true, Q is false, and R is true?

  1. True

  2. False


Correct Option: A
Explanation:

Using the truth table for the logical connectives, we can determine that the compound proposition is true.

Which of the following is a valid logical argument?

  1. If it is raining, then the ground is wet.

  2. The ground is wet, therefore it is raining.

  3. If it is raining, then the sky is blue.

  4. The sky is blue, therefore it is raining.


Correct Option: A
Explanation:

A valid logical argument is one in which the conclusion follows logically from the premises.

What is the difference between a sound and an unsound logical argument?

  1. A sound argument has true premises and a true conclusion.

  2. An unsound argument has false premises and a false conclusion.

  3. A sound argument has true premises and a false conclusion.

  4. An unsound argument has false premises and a true conclusion.


Correct Option: A
Explanation:

A sound logical argument is one in which the premises are true and the conclusion follows logically from the premises.

Which of the following is an example of a sound logical argument?

  1. All men are mortal.

  2. Socrates is a man.

  3. Therefore, Socrates is mortal.

  4. All dogs are mammals.

  5. Cats are not dogs.

  6. Therefore, cats are not mammals.


Correct Option:
Explanation:

This is a sound logical argument because the premises are true and the conclusion follows logically from the premises.

Which of the following is an example of an unsound logical argument?

  1. All birds can fly.

  2. Penguins are birds.

  3. Therefore, penguins can fly.

  4. All fruits contain seeds.

  5. Tomatoes are fruits.

  6. Therefore, tomatoes contain seeds.


Correct Option:
Explanation:

This is an unsound logical argument because the premises are true but the conclusion does not follow logically from the premises.

What is the converse of the proposition "If it is raining, then the ground is wet"?

  1. If the ground is wet, then it is raining.

  2. If it is not raining, then the ground is not wet.

  3. If the ground is not wet, then it is not raining.

  4. If it is raining, then the ground is not wet.


Correct Option: A
Explanation:

The converse of a proposition is formed by switching the hypothesis and the conclusion.

What is the inverse of the proposition "If it is raining, then the ground is wet"?

  1. If it is not raining, then the ground is not wet.

  2. If the ground is wet, then it is raining.

  3. If the ground is not wet, then it is not raining.

  4. If it is raining, then the ground is not wet.


Correct Option: A
Explanation:

The inverse of a proposition is formed by negating both the hypothesis and the conclusion.

What is the contrapositive of the proposition "If it is raining, then the ground is wet"?

  1. If the ground is wet, then it is raining.

  2. If it is not raining, then the ground is not wet.

  3. If the ground is not wet, then it is not raining.

  4. If it is raining, then the ground is not wet.


Correct Option: C
Explanation:

The contrapositive of a proposition is formed by negating both the hypothesis and the conclusion, and then switching them.

Which of the following is a tautology?

  1. (P ∨ ¬P)

  2. (P ∧ ¬P)

  3. (P → Q) ∨ (¬P → Q)

  4. (P → Q) ∧ (¬P → ¬Q)


Correct Option: A
Explanation:

A tautology is a compound proposition that is always true, regardless of the truth values of its component propositions.

Which of the following is a contradiction?

  1. (P ∨ ¬P)

  2. (P ∧ ¬P)

  3. (P → Q) ∨ (¬P → Q)

  4. (P → Q) ∧ (¬P → ¬Q)


Correct Option: B
Explanation:

A contradiction is a compound proposition that is always false, regardless of the truth values of its component propositions.

What is the law of detachment?

  1. If P → Q and P, then Q.

  2. If P → Q and ¬Q, then ¬P.

  3. If P ∨ Q and P, then Q.

  4. If P ∨ Q and ¬P, then Q.


Correct Option: A
Explanation:

The law of detachment is a rule of inference that allows us to conclude Q from P → Q and P.

What is the law of syllogism?

  1. If P → Q and Q → R, then P → R.

  2. If P → Q and ¬Q, then ¬P.

  3. If P ∨ Q and P, then Q.

  4. If P ∨ Q and ¬P, then Q.


Correct Option: A
Explanation:

The law of syllogism is a rule of inference that allows us to conclude P → R from P → Q and Q → R.

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