Banking Notes / Reasoning & Puzzles / Chapter 2
Chapter 2 of 24

Syllogism

The Venn diagram method for solving 'All, Some, No' statement-conclusion questions accurately, including the tricky either/or complementary pair rule.

📖 ~10 min read 🧩 Banking Reasoning & Puzzles

Introduction

Syllogism gives two or more statements about the relationship between categories (e.g., "All cats are animals") and asks which conclusions definitely follow. The most reliable method is drawing every possible Venn diagram for the statements and checking which conclusion holds true in all of them.

The Four Statement Types

StatementMeaning
All A are BEvery A is inside B (A is fully inside B, though B can be larger)
Some A are BA and B overlap partially — at least one A is a B
No A is BA and B are completely separate, no overlap at all
Some A are not BAt least one A lies outside B
Q. Statements: All pens are books. Some books are pencils.
Conclusions: I. Some pencils are pens. II. Some books are pens.
"All pens are books" means the pens circle sits fully inside the books circle — so Conclusion II ("Some books are pens") is always true, since every pen is a book. Conclusion I doesn't necessarily follow because "some books are pencils" doesn't guarantee pencils overlap with pens specifically. Answer: Only Conclusion II follows.

The Either-Or Case

When two conclusions are a complementary pair (e.g., "Some A are B" and "No A is B", or "All A are B" and "Some A are not B") and neither follows individually, but together they cover every possibility — mark "Either I or II follows."
⚠️ Key Insight: Never assume a conclusion is true just because it "seems likely" — draw the alternate (least obvious) Venn diagram possibility for each statement combination; if the conclusion fails in even one valid diagram, it does not follow.
✅ Practice Focus: Drawing all valid Venn diagrams for two-statement combinations · Testing conclusions against every possible diagram · Recognising complementary either-or conclusion pairs.

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