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Set-relation reasoning with overlap: given 'Some dreams are nights' and 'Some nights are days', decide which conclusions necessarily follow (All days are either nights or dreams; Some days are nights)

Difficulty: Easy

Correct Answer: Only conclusion II follows

Explanation:


Given data

  • Premise 1: Some Dreams ∩ Nights ≠ ∅.
  • Premise 2: Some Nights ∩ Days ≠ ∅.
  • Conclusions:
    • I: All Days ⊆ (Nights ∪ Dreams).
    • II: Some Days ∩ Nights ≠ ∅.


Concept/Approach (why this method)

Particular ('some') statements guarantee existence of overlap; they do not justify sweeping universals about entire sets.


Step-by-Step calculation / logic
1) From Premise 2, there exists at least one element that is both Day and Night ⇒ II is necessarily true.2) Nothing links all Days to Nights or Dreams ⇒ I is not compelled and is overgeneralization.


Verification/Alternative

Construct sets where only a small portion of Days overlap Nights; I fails while II holds.


Common pitfalls

  • Treating 'some' as 'all'.


Final Answer
Only conclusion II follows.

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