Paper I - Logical Reasoning
Logical Reasoning tests valid deduction rather than real-world plausibility. Core areas include syllogism, analogies, series, coding-decoding, blood relations, direction sense, statement-assumption, and argument evaluation.
Rules to apply
- In syllogism, use Venn or Euler diagrams; a conclusion is valid only if it must be true in every diagram consistent with the premises.
- 'All A are B' does not imply 'All B are A'. 'Some A are B' does not imply 'Some B are not A'.
- In assumption questions, the assumption is an unstated necessary premise, not a restatement.
- In direction sense, track turns relative to current facing and draw axes.
- In coding, test letter positions, reversals and shifts separately.
Worked example
Premises: All engineers are graduates; some graduates are managers. Is 'some engineers are managers' valid? No. The managers who are graduates may lie outside the engineer set. The premise only places engineers inside graduates; it does not force an overlap with managers. A diagram with engineers inside graduates and managers partly outside graduates satisfies both premises and makes the conclusion false.
Traps that cost marks
Converting 'all' into 'all'; assuming 'some' means 'some but not all'; using plausible content to override logical form; missing 'only', 'unless' and 'no'.