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[Propositional Logic]

Assertion (A): The Equivalence expression is p ↔ q.

Reason (R): An Equivalence Statement always gives the final result as Contingencies.

ID: #24957 Competency focused Practice Questions ISC Class XII Computer Science 4 views
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Competency focused Practice Questions ISC Class XII Computer ScienceTopic

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  • A Both A and R are true, and R is the correct explanation of A.
  • B Both A and R are true, but R is not the correct explanation of A.
  • C A is true, but R is false.
  • D A is false, but R is true.
Correct Answer: Option C

Explanation

[Propositional Logic]

Assertion (A): The Equivalence expression is p ↔ q.

Reason (R): An Equivalence Statement always gives the final result as Contingencies.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Correct Answer: (c)

Step 1: Understanding Assertion (A)

The Equivalence expression is p ↔ q

This statement is true.

In propositional logic:

p ↔ q

is called the:

  • Biconditional statement
  • Logical equivalence statement

It means:

p if and only if q

Truth Table of p ↔ q:

p q p ↔ q
T T T
T F F
F T F
F F T

Therefore:

Assertion (A) is TRUE

Step 2: Understanding Reason (R)

An Equivalence Statement always gives the final result as Contingencies.

This statement is false.

Why?

In propositional logic:

  • Tautology → Always true
  • Contradiction → Always false
  • Contingency → Sometimes true and sometimes false

An equivalence expression does NOT always produce contingency.

Depending on the logical statements involved, it may result in:

  • Tautology
  • Contradiction
  • Contingency

Example:

(p → q) ↔ (~q → ~p)

This expression is always TRUE, so it becomes a:

Tautology

Hence the reason statement is incorrect.

Reason (R) is FALSE

Important Concept:

Logical Result Meaning
Tautology Always True
Contradiction Always False
Contingency Sometimes True, Sometimes False

Final Conclusion:

  • Assertion (A) → True ✅
  • Reason (R) → False ❌
Correct Answer: (c)

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