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Question

Assume that a Creative ($C$) person will Succeed ($S$) if the person is also Disciplined ($D$), but will not succeed otherwise. Now, consider the following statements:
(i) $C \land S \Leftrightarrow D$
(ii) $C \Rightarrow (S \Leftrightarrow D)$
(iii) $C \Leftrightarrow ((D \Rightarrow S) \lor \neg S)$

Which of the following options is correct?

The correct answer is
Only (ii) is TRUE

This problem involves analyzing logical statements derived from a given condition about creativity, success, and discipline.

Problem Setup

Let the propositions be:

  • $C$: The person is Creative.
  • $S$: The person will Succeed.
  • $D$: The person is Disciplined.

The core condition stated is: "A Creative ($C$) person will Succeed ($S$) if the person is also Disciplined ($D$), but will not succeed otherwise." This translates to: If a person is Creative ($C$ is True), then they Succeed ($S$) if and only if they are Disciplined ($D$). Logically, this is represented as: $C \Rightarrow (S \Leftrightarrow D)$

This core condition must hold true for any valid scenario described by the problem.

Analysis of Statements

Statement (i): $C \land S \Leftrightarrow D$

To check if this statement is always true according to the problem's condition, let's consider a case where the core condition $C \Rightarrow (S \Leftrightarrow D)$ holds, but statement (i) might not.

Consider a scenario where the person is not creative ($C$ is False) but is disciplined ($D$ is True) and succeeds ($S$ is True).

  • Core condition check: $C \Rightarrow (S \Leftrightarrow D)$ becomes $F \Rightarrow (T \Leftrightarrow T)$, which is $F \Rightarrow T$, which is TRUE. The core condition holds.
  • Statement (i) check: $C \land S \Leftrightarrow D$ becomes $F \land T \Leftrightarrow T$, which is $F \Leftrightarrow T$, which is FALSE.

Since we found a valid scenario where statement (i) is False, statement (i) is not always true. Statement (i) is FALSE.

Statement (ii): $C \Rightarrow (S \Leftrightarrow D)$

This statement is the direct logical translation of the problem's core condition ("A Creative ($C$) person will Succeed ($S$) if the person is also Disciplined ($D$), but will not succeed otherwise").

Therefore, statement (ii) must be TRUE based on the problem's definition.

Statement (iii): $C \Leftrightarrow ((D \Rightarrow S) \lor \neg S)$

Let's simplify the right side of the equivalence: $(D \Rightarrow S) \lor \neg S$. Using the logical equivalence $P \Rightarrow Q \equiv \neg P \lor Q$, we get:

  • $(\neg D \lor S) \lor \neg S$
  • $\equiv \neg D \lor (S \lor \neg S)$ (Associativity of $\lor$)
  • $\equiv \neg D \lor T$ (Since $S \lor \neg S$ is a tautology, always True)
  • $\equiv T$ (Since $\neg D \lor T$ is always True)

So, statement (iii) simplifies to $C \Leftrightarrow T$, which means $C$ must always be True.

However, the problem does not state that only creative people exist or are considered. A person can be not creative ($C$ is False).

Let's use the scenario from statement (i) analysis: $C=F, D=T, S=T$. The core condition holds.

  • Statement (iii) check: $C \Leftrightarrow ((D \Rightarrow S) \lor \neg S)$ becomes $F \Leftrightarrow T$, which is FALSE.

Since we found a valid scenario where statement (iii) is False, statement (iii) is not always true. Statement (iii) is FALSE.

Conclusion

Based on the analysis:

  • Statement (i) is FALSE.
  • Statement (ii) is TRUE.
  • Statement (iii) is FALSE.

Therefore, only statement (ii) is TRUE.

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Important Questions from Propositional Logic

  1. Let $x$ and $y$ be two propositions. Which of the following statements is a tautology /are tautologies?
  2. Let $p$ and $q$ be any two propositions. Consider the following propositional statements.
    $S_1: p \to q$            $S_2: \neg p \land q$              $S_3: \neg p \lor q$             $S_4 : \neg p \lor \neg q$
    where $\land$ denotes conjunction (AND operation), $\lor$ denotes disjunction (OR operation), and $\neg$ denotes negation (NOT operation). Which one of the following options is correct?
    (Note: $\equiv$ denotes logical equivalence)

  3. Which of the following logical implications are tautology? 

    A. $[\sim p \land (p \lor q)] \rightarrow q$

     B. $\sim p \rightarrow (p \rightarrow q)$ 

    C. $[p \land (p \rightarrow q)] \rightarrow q$ 

    D. $\sim (p \rightarrow q) \rightarrow q$ 

    Choose the correct answer from the options given below:

  4. Sentence $X$ is said to entail Sentence $Y$ if whenever $X$ is $TRUE$, $Y$ also must hold $TRUE$.

    Which of the following statements is/are correct if $X$ entails $Y$?
  5. Let P denote "She is intelligent" and let Q denote "She is happy."
    Given below are the statements:
    (a) If She is intelligent, then She is unhappy.
    (b) She is neither intelligent nor happy.
    (c) It is necessary to be not intelligent in order to be happy.
    (d) To be not intelligent is to be unhappy.
    Which of the following is correct Propositional expression for the above statements:
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