Reasoning Ability: Rules Over Intuition
What the section tests
Reasoning Ability in the BSCB Clerk paper checks rule-based thinking rather than prior knowledge: syllogisms, puzzles and seating arrangements, blood relations, coding-decoding, inequalities, direction sense, alphanumeric series and input-output. Nearly every question is solved by converting the statement into a fixed structure and then applying that structure mechanically.
Core rules
- Syllogism: work only from the diagram, never from real-world truth. 'All A are B' converts to 'Some B are A'; 'Some A are B' also gives 'Some B are A'; 'No A is B' converts to 'No B is A'. A conclusion is true only if it holds in every possible Venn diagram.
- Inequalities: a chain such as A > B ≥ C = D > E gives A > C, B ≥ D and A > E. Conclusions with the same direction combine; opposite directions give no definite relation.
- Coding-decoding: test letter-position shifts first (+1, −2), then reversal, then letter-to-number mapping.
- Seating arrangements: fix the person with the most constraints, draw positions, and mark facing direction explicitly before adding anyone else.
Worked example
Statements: All clerks are bankers. Some bankers are officers. Candidate conclusion: Some clerks are officers. Draw the 'clerks' circle inside 'bankers'; 'officers' overlaps 'bankers' at a place that need not touch clerks. Since one valid diagram has no clerk inside officers, the conclusion is not definite - it does not follow. But 'Some officers are bankers' does follow, because the overlap can be read in either direction.
Traps that cost marks
Treating 'some' as 'some but not all'; reversing 'All A are B' into 'All B are A'; ignoring either-or pairs in inequality questions; and missing the second possibility in 'only a few' statements, which this paper does use. In puzzles, one unplaced person usually means a clue was read with the wrong facing direction.