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JEE Main 2021
Mathematical Reasoning
Mathematical Reasoning
Easy

Question

Let p, q, r be three statements such that the truth value of (p \wedge q) \to (\simq \vee r) is F. Then the truth values of p, q, r are respectively :

Options

Solution

Key Concepts and Formulas

  • The implication ABA \to B is false only when AA is true and BB is false.
  • The conjunction ABA \wedge B is true only when both AA and BB are true.
  • The disjunction ABA \vee B is false only when both AA and BB are false.
  • The negation of a true statement is false, and the negation of a false statement is true.

Step-by-Step Solution

Step 1: Analyze the given information.

We are given that (pq)(qr)(p \wedge q) \to (\sim q \vee r) is false. We need to determine the truth values of pp, qq, and rr.

Step 2: Apply the implication rule.

Since the implication (pq)(qr)(p \wedge q) \to (\sim q \vee r) is false, it must be the case that the antecedent (pq)(p \wedge q) is true and the consequent (qr)(\sim q \vee r) is false. (pq)=T(p \wedge q) = T (qr)=F(\sim q \vee r) = F

Step 3: Determine the truth values of pp and qq.

Since pqp \wedge q is true, both pp and qq must be true. p=Tp = T q=Tq = T

Step 4: Determine the truth value of q\sim q.

Since qq is true, its negation q\sim q is false. q=F\sim q = F

Step 5: Determine the truth value of rr.

Since qr\sim q \vee r is false, and we know that q\sim q is false, then rr must also be false. r=Fr = F

Step 6: Summarize the truth values of pp, qq, and rr.

We have found that pp is true, qq is true, and rr is false. Therefore, the truth values of p,q,rp, q, r are T, T, F respectively.

Common Mistakes & Tips

  • Remember the truth table for implication. ABA \to B is only false when A is true and B is false.
  • Be careful with negations. If qq is true, then q\sim q is false, and vice versa.
  • It is useful to write out the truth tables for AND, OR, NOT, and IMPLICATION.

Summary

We are given that (pq)(qr)(p \wedge q) \to (\sim q \vee r) is false. This means that pqp \wedge q must be true and qr\sim q \vee r must be false. Since pqp \wedge q is true, both pp and qq must be true. Since qq is true, q\sim q is false. Since qr\sim q \vee r is false and q\sim q is false, rr must also be false. Therefore, pp is true, qq is true, and rr is false.

Final Answer

The final answer is \boxed{T, T, F}, which corresponds to option (D).

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