IQ Data Sufficiency Logic Truth Competitive Exams
50 questions · IQ Logic and Reasoning
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Question 1 of 50
Which of the following is a tautology (always true)?
Explanationp ∨ ¬p is true whatever the value of p; p ∧ ¬p and p ↔ ¬p are always false.
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Question 2 of 50
What is the average of three integers a, b and c? (each from 1 to 20) I. a + b + c = 36. II. a = 10 and b = 12.
ExplanationStatement I alone gives a single answer; Statement II alone does not.
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Question 3 of 50
Consider the following 4 statements. Statement 1: 'Exactly 3 of these 4 statements are false.' Statement 2: 'Exactly 2 of these 4 statements are false.' Statement 3: 'Exactly 3 of these 4 statements are false.' Statement 4: 'Exactly 1 of these 4 statements is false.' Which statements are true?
ExplanationAssume the number of false statements is f; statement i is true only if f equals its claimed number. Exactly 4 statement(s) are false in the only consistent case, so the true statements are: none of the statements is true.
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Question 4 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B is truthful'. B says: 'A and C are of the same type'. C says: 'B is a liar'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: C only.
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Question 5 of 50
What is the value of the integer x? (x is between -10 and 10) I. x² = 9. II. x > 0.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 6 of 50
What is the speed s = d / t of a car? (distance d in km from 1 to 200, time t in hours from 1 to 10) I. d = 120 km. II. t = 2 hours.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 7 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B is a liar'. B says: 'at least one of A and C is truthful'. C says: 'A and B are of different types'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: B and C are truthful.
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Question 8 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'at least one of B and C is truthful'. B says: 'A and C are of different types'. C says: 'B is truthful'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: None of them is truthful.
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Question 9 of 50
What is the value of the positive integer x (at most 30)? I. x is a prime number. II. x < 10.
ExplanationEven together the statements leave more than one possible answer.
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Question 10 of 50
If p is True and q is False, the truth value of the biconditional p ↔ q is
ExplanationA biconditional is true only when p and q have the same truth value; here they differ.
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Question 11 of 50
The conditional p → q is logically equivalent to
ExplanationBoth are false only when p is true and q is false.
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Question 12 of 50
By De Morgan's law, ¬(p ∨ q) is equivalent to
ExplanationThe negation of a disjunction is the conjunction of the negations.
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Question 13 of 50
Is x greater than y? (x and y are positive integers) I. x = y + 3. II. x² > y².
ExplanationEach statement alone gives a single answer.
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Question 14 of 50
If p → q is true and q is false, then p must be
ExplanationBy modus tollens: if p → q and ¬q, then ¬p.
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Question 15 of 50
What is the value of xy? (x and y are positive integers) I. x + y = 5. II. x − y = 1.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 16 of 50
Consider the following 4 statements. Statement 1: 'Exactly 2 of these 4 statements are false.' Statement 2: 'Exactly 4 of these 4 statements are false.' Statement 3: 'Exactly 2 of these 4 statements are false.' Statement 4: 'Exactly 1 of these 4 statements is false.' Which statements are true?
ExplanationAssume the number of false statements is f; statement i is true only if f equals its claimed number. Exactly 2 statement(s) are false in the only consistent case, so the true statements are: statements 1 and 3 are true.
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Question 17 of 50
The negation of the conditional p → q is
Explanationp → q is false exactly when p is true and q is false, which is p ∧ ¬q (verified by truth table).
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Question 18 of 50
Is Ali taller than Bilal? (heights are distinct integers in cm from 150 to 155) I. Ali is taller than Chand. II. Chand is taller than Bilal.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 19 of 50
Is the positive integer x even? I. x² is even. II. x + 1 is odd.
ExplanationEach statement alone gives a single answer.
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Question 20 of 50
'The team wins only if it plays well' is symbolised as (w = wins, p = plays well)
Explanation'A only if B' means A → B: if the team wins, it must have played well.
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Question 21 of 50
What is the cost p of one pen? (pen price p and pencil price q are positive integers up to 50) I. 3p + 2q = 24. II. p + q = 9.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 22 of 50
By De Morgan's law, ¬(p ∧ q) is equivalent to
ExplanationThe negation of a conjunction is the disjunction of the negations.
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Question 23 of 50
What is the value of x? (x and y are integers from 1 to 20) I. x + y = 10. II. x − y = 2.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 24 of 50
Consider the following 4 statements. Statement 1: 'Exactly 1 of these 4 statements is false.' Statement 2: 'Exactly 0 of these 4 statements are false.' Statement 3: 'Exactly 4 of these 4 statements are false.' Statement 4: 'Exactly 3 of these 4 statements are false.' Which statements are true?
ExplanationAssume the number of false statements is f; statement i is true only if f equals its claimed number. Exactly 3 statement(s) are false in the only consistent case, so the true statements are: only statement 4 is true.
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Question 25 of 50
The contrapositive of 'If it rains, the match is cancelled' is
ExplanationThe contrapositive of p → q is ¬q → ¬p and is logically equivalent to the original statement.
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Question 26 of 50
What is the value of x? (x is a positive integer up to 20) I. x² − 5x + 6 = 0. II. x > 2.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 27 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B is a liar'. B says: 'A and C are of the same type'. C says: 'B is truthful'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: A only.
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Question 28 of 50
Consider the following 4 statements. Statement 1: 'Exactly 3 of these 4 statements are false.' Statement 2: 'Exactly 4 of these 4 statements are false.' Statement 3: 'Exactly 4 of these 4 statements are false.' Statement 4: 'Exactly 2 of these 4 statements are false.' Which statements are true?
ExplanationAssume the number of false statements is f; statement i is true only if f equals its claimed number. Exactly 3 statement(s) are false in the only consistent case, so the true statements are: only statement 1 is true.
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Question 29 of 50
Is the integer p (between 2 and 30) a prime number? I. p is odd. II. p is less than 4.
ExplanationStatement II alone gives a single answer; Statement I alone does not.
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Question 30 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B is truthful'. B says: 'both A and C are liars'. C says: 'both A and B are liars'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: C only.
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Question 31 of 50
Is the positive integer x (at most 100) divisible by 4? I. x is divisible by 8. II. x is divisible by 12.
ExplanationEach statement alone gives a single answer.
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Question 32 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B is truthful'. B says: 'at least one of A and C is truthful'. C says: 'both A and B are liars'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: A and B are truthful.
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Question 33 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B and C are of the same type'. B says: 'at least one of A and C is truthful'. C says: 'B is truthful'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: All three are truthful.
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Question 34 of 50
What is A's age (in whole years)? I. A is 5 years older than B. II. B is 20 years old.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 35 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'B and C are of the same type'. B says: 'A is a liar'. C says: 'B is a liar'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: B only.
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Question 36 of 50
If p is True and q is False, the truth value of the conditional p → q is
ExplanationA conditional is false only when the antecedent is true and the consequent is false. Here p → q = False.
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Question 37 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'at least one of B and C is truthful'. B says: 'both A and C are liars'. C says: 'A is truthful'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: A and C are truthful.
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Question 38 of 50
Is the positive integer x (at most 60) a multiple of 3? I. x is a multiple of 6. II. x is even.
ExplanationStatement I alone gives a single answer; Statement II alone does not.
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Question 39 of 50
How many students are in a class? (the number is a positive integer up to 100) I. The number is greater than 30, less than 40 and a multiple of 8. II. The number is even.
ExplanationStatement I alone gives a single answer; Statement II alone does not.
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Question 40 of 50
The inverse of 'If a number is divisible by 4, then it is even' is
ExplanationThe inverse of p → q is ¬p → ¬q (both parts are negated, order kept).
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Question 41 of 50
Consider the following 4 statements. Statement 1: 'Exactly 1 of these 4 statements is false.' Statement 2: 'Exactly 4 of these 4 statements are false.' Statement 3: 'Exactly 3 of these 4 statements are false.' Statement 4: 'Exactly 0 of these 4 statements are false.' Which statements are true?
ExplanationAssume the number of false statements is f; statement i is true only if f equals its claimed number. Exactly 3 statement(s) are false in the only consistent case, so the true statements are: only statement 3 is true.
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Question 42 of 50
Is the product ab positive? (a and b are non-zero integers between -10 and 10) I. a > 0. II. b > 0.
ExplanationNeither statement alone gives a single answer, but together they fix the answer.
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Question 43 of 50
If p is True and q is True, the truth value of the exclusive or p ⊕ q is
ExplanationExclusive or is true only when exactly one of the two is true.
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Question 44 of 50
'p unless q' is equivalent to
Explanation'p unless q' means: if q does not happen, then p; this equals p ∨ q (verified by truth table).
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Question 45 of 50
Is x less than 5? (x is a positive integer up to 10) I. x² < 30. II. x is a prime number less than 7.
ExplanationEven together the statements leave more than one possible answer.
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Question 46 of 50
The converse of 'If x is even, then x² is even' is
ExplanationThe converse of p → q is q → p (the parts are swapped).
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Question 47 of 50
If p is False and q is False, the truth value of p → q is
ExplanationA conditional with a false antecedent is true, so p → q = True.
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Question 48 of 50
What is the perimeter of a rectangle with integer sides (length l, width w, each from 1 to 30)? I. l = 6 and the area is 24. II. l − w = 2.
ExplanationStatement I alone gives a single answer; Statement II alone does not.
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Question 49 of 50
Each of A, B and C is either always truthful or always a liar. A says: 'C is truthful'. B says: 'both A and C are liars'. C says: 'both A and B are liars'. Who is truthful?
ExplanationTest each possible combination of truthful/liar. Only one assignment makes every statement agree with its speaker's type: B only.
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Question 50 of 50
Is the sum of two positive integers a and b (each up to 20) even? I. Both a and b are odd. II. The product ab is odd.
ExplanationEach statement alone gives a single answer.
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