1. If all swans are birds, some birds are white, and no white creature can fly at night, which of the following must be true?
A) Some swans cannot fly at night
B) All swans are white
C) No bird can fly at night
D) Some birds may fly at night
B) All swans are white
C) No bird can fly at night
D) Some birds may fly at night
Answer: A
Explanation: From the premises, swans ⊆ birds. Some birds are white (not necessarily swans). “No white creature can fly at night.” If any swan is white, it cannot fly at night; if not white, no restriction. So at least some swans (those that may be white) cannot fly at night.
Explanation: From the premises, swans ⊆ birds. Some birds are white (not necessarily swans). “No white creature can fly at night.” If any swan is white, it cannot fly at night; if not white, no restriction. So at least some swans (those that may be white) cannot fly at night.
2. Statement: If it rains, the ground will be wet. The ground is wet.
Which inference is logically valid?
Which inference is logically valid?
A) It rained
B) It may or may not have rained
C) It did not rain
D) The statement is invalid
B) It may or may not have rained
C) It did not rain
D) The statement is invalid
Answer: B
Explanation: Wet ground does not imply it rained (could be sprinklers). Affirming the consequent is a fallacy; only possibility remains that rain is one cause.
Explanation: Wet ground does not imply it rained (could be sprinklers). Affirming the consequent is a fallacy; only possibility remains that rain is one cause.
3. Five students sit in a row facing north. P is left of Q but right of R. S is at extreme left. T is right of Q. Who is in the middle?
A) P
B) Q
C) R
D) T
B) Q
C) R
D) T
Answer: B
Explanation: Order: S – R – P – Q – T. The middle is Q.
Explanation: Order: S – R – P – Q – T. The middle is Q.
4. Premise: “Every efficient lawyer reads daily.” “Some who read daily are not efficient.” What follows?
A) All who read daily are lawyers
B) Some who read daily may be inefficient lawyers
C) Reading daily is sufficient for efficiency
D) Efficiency implies not reading daily
B) Some who read daily may be inefficient lawyers
C) Reading daily is sufficient for efficiency
D) Efficiency implies not reading daily
Answer: B
Explanation: First says: Efficient lawyer → reads daily. Second: (reads daily, not efficient). So at least one daily reader lacks efficiency; could be lawyer or not. Option B is correct.
Explanation: First says: Efficient lawyer → reads daily. Second: (reads daily, not efficient). So at least one daily reader lacks efficiency; could be lawyer or not. Option B is correct.
5. Which argument is structurally identical to: “If A then B. Not A. Therefore not B.”?
A) If snow, then cold. No cold, therefore no snow.
B) If he studies, he passes. He didn’t study; thus may not pass.
C) If music plays, lights shine. No music, thus no lights.
D) If road blocked, we detour. Road free, so we won’t detour.
B) If he studies, he passes. He didn’t study; thus may not pass.
C) If music plays, lights shine. No music, thus no lights.
D) If road blocked, we detour. Road free, so we won’t detour.
Answer: C
Explanation: From “If A then B,” it’s wrong to say “If not A then not B”, that mistake is called denying the antecedent, and that’s what Option C shows.
Explanation: From “If A then B,” it’s wrong to say “If not A then not B”, that mistake is called denying the antecedent, and that’s what Option C shows.
6. A puzzle: Four boxes (W,X,Y,Z). Only one has treasure. Clues:
- Treasure not in W or X.
- If in Y, then clue 3 is false.
- Treasure in X or Z.
Where is the treasure?
A) W
B) X
C) Y
D) Z
B) X
C) Y
D) Z
Answer: D
Explanation: Clue (1) rules out W and X, so only Y or Z can be true.
Explanation: Clue (1) rules out W and X, so only Y or Z can be true.
If Y were true, clue (3) would be false, which forces Z to be false—giving a messy, non-unique setup.
With Z true, clue (3) is true and everything stays consistent, yielding a single clear solution.
With Z true, clue (3) is true and everything stays consistent, yielding a single clear solution.
Only Z fits all without conditional trick.
7. If some poets are philosophers, all philosophers are dreamers, and no dreamer is idle, which is a valid conclusion?
A) Some poets are not idle
B) All poets are dreamers
C) All dreamers are philosophers
D) Some philosophers may be poets
B) All poets are dreamers
C) All dreamers are philosophers
D) Some philosophers may be poets
Answer: D
Explanation:
Explanation:
Correct: D.
Since some poets are philosophers and all philosophers are dreamers, those poets-who-are-philosophers are definitely dreamers—so some poets are dreamers.
Since some poets are philosophers and all philosophers are dreamers, those poets-who-are-philosophers are definitely dreamers—so some poets are dreamers.
8. Identify the flaw: “All judges are honest. Some officials are judges. Therefore all officials are honest.”
A) Invalid conversion
B) Composition fallacy
C) Post hoc
D) Denying consequent
B) Composition fallacy
C) Post hoc
D) Denying consequent
Answer: B
Explanation: Argument assumes property of part (judges) extends to whole set (officials).
Explanation: Argument assumes property of part (judges) extends to whole set (officials).
9. A circular arrangement of six chairs labelled A–F clockwise. B sits two places right of A. D opposite B. C between A and D. Who sits left of E?
A) A
B) B
C) F
D) C
B) B
C) F
D) C
Answer: C
Explanation: Arrange carefully: A seat1; B seat3; D seat6; C between A & D = seat2; remaining seats E seat4, F seat5. Left of E (seat4) is F.
Explanation: Arrange carefully: A seat1; B seat3; D seat6; C between A & D = seat2; remaining seats E seat4, F seat5. Left of E (seat4) is F.
10. Statement: Either the contract is void or the offer is invalid. The offer is valid. Conclusion?
A) The contract is void
B) Offer invalid
C) Neither void nor invalid
D) Data inadequate
B) Offer invalid
C) Neither void nor invalid
D) Data inadequate
Answer: A
Explanation: Since it’s “V or I” and not-I is true, V has to be true.
Explanation: Since it’s “V or I” and not-I is true, V has to be true.
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Ruchika Mohapatra
Contributing author
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