Syllogisms & Deductive Logic

Syllogisms test formal deductive logic. A conclusion is definitively true ONLY if it holds in 100% of all possible valid Venn diagrams. If even one counter-example diagram disproves it, the conclusion does not follow.

Exam Frequency: 4 to 5 questions in Bank PO/Clerk and TCS NQT

Essential Formulas & Shortcut Rules

"Only a few A are B" = "Some A are B" AND "Some A are not B"

Crucial modern banking rule.

Either-Or Condition: (1) Same subject-predicate, (2) Both individual conclusions false, (3) Complementary pair (Some + No OR All + Some Not)

Conditions required for an Either-Or relationship.

Worked Step-by-Step Examples

Example 1: Statements: All apples are fruits. Some fruits are sweet. No sweet is bitter. Conclusions: I. Some fruits are not bitter. II. All apples being sweet is a possibility.

Step-by-Step Mathematical Derivation:

•Analyzing Conclusion I: The portion of "fruits" that are "sweet" cannot be "bitter" because No sweet is bitter. Thus, at least those fruits are definitely not bitter. Conclusion I follows.

•Analyzing Conclusion II: Can all apples be sweet without violating any statement? Yes, apples can overlap sweet completely within fruits without touching bitter. Conclusion II follows.

Answer: Both conclusions I and II follow

💡 Speed Shortcut: For possibility questions, attempt to draw one valid diagram where the condition is satisfied without breaking rules.

Common Exam Traps to Avoid

✕Assuming real-world truth instead of strictly adhering to the stated premise.
✕Treating "Some A are B" as implying that "Some A are NOT B" in classical logic.

Interactive Practice Drill (2 Questions)

Instant Explanations • Timed

Assessment Simulator

Syllogisms & Deductive Logic Practice Drill

2 Questions • No negative marking

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1Syllogisms & Deductive Logic

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Statements: 1. All laptops are devices. 2. Some devices are gadgets. 3. No gadget is mechanical. Conclusions: I. Some devices are not mechanical. II. No laptop is mechanical.

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