Logical Reasoning and Problem Solving
Logical Reasoning and Problem Solving tests valid inference, conditional reasoning, sequencing, and the ability to separate evidence from assumption. The exam uses short scenarios and rules; the correct answer follows from the stated premises even when it is not the most dramatic option.
Core rules
- In a conditional 'If P, then Q,' P is sufficient for Q; Q is necessary for P. The valid inference from not-Q is not-P.
- Invalid forms: affirming the consequent (Q, therefore P) and denying the antecedent (not-P, therefore not-Q).
- Distinguish correlation from causation; a rise in one number alongside another does not prove one caused the other.
- For ordering problems, draw a simple line or table and place fixed items first.
- For assumptions, ask what must be true for the conclusion to hold, not what is merely plausible.
Worked example
Rule: 'If the gate is locked, the alarm is armed.' You learn the alarm is not armed. Valid conclusion: the gate is not locked. This is modus tollens. If you instead learn the alarm is armed, you cannot conclude the gate is locked; other conditions could arm the alarm. That is affirming the consequent.
Traps that cost marks
Reversing a conditional; treating a necessary condition as sufficient; bringing in real-world knowledge that the prompt does not state; and choosing an answer that is possible rather than required. In 'must be true' items, test each option against the premises and eliminate any option that could be false under those premises.