Syllogism — Cars, Jeeps, Boxes, and Pens Statements: • Some cars are jeeps. • All the boxes are jeeps. • All the pens are cars. Conclusions: (1) Some cars are boxes. (2) No pen is a jeep. (3) Some boxes are cars.

Difficulty: Medium

Correct Answer: None of three

Explanation:


Introduction / Context:
This question mixes “some” with two universal statements. The danger is to infer overlaps between Cars and Boxes or Pens and Jeeps without explicit compulsion.


Given Data / Assumptions:

  • Some Cars (C) are Jeeps (J): C∩J ≠ ∅.
  • All Boxes (B) are Jeeps (J): B ⊆ J.
  • All Pens (P) are Cars (C): P ⊆ C.
  • Conclusions: (1) Some C are B. (2) No P is J. (3) Some B are C.


Concept / Approach:
To prove “some X are Y,” we need a compelled intersection. To prove “No X is Y,” we need a compelled disjointness. Here, neither is forced between Cars and Boxes nor between Pens and Jeeps.


Step-by-Step Solution:

Because B ⊆ J and only “some” Cars are Jeeps, Boxes could lie wholly in the Jeep region disjoint from the Car portion. Hence neither “Some cars are boxes” nor “Some boxes are cars” is compelled.All Pens are Cars, yet some Cars are Jeeps. Pens might be in the non-Jeep area of Cars or could also overlap Jeeps; premises do not fix this. Therefore “No pen is a jeep” is not guaranteed.


Verification / Alternative check:
Draw J as a set. Place B entirely inside J but outside C. Place C partially overlapping J (to satisfy “some C are J”) and put P inside the C area that is outside J. All premises hold; (1), (2), and (3) are false simultaneously, proving that none of the three conclusions must follow.


Why Other Options Are Wrong:

  • Pairs like (1)&(2) or (1)&(3) assume overlaps not forced by the statements.
  • (2)&(3) also fails because (2) is not compelled and (3) is not compelled either.


Common Pitfalls:
Assuming that two sets contained in a third must overlap each other. Subsets of a common superset can still be disjoint.


Final Answer:
None of three

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