Logical Reasoning: Pattern Detection and Deduction
Logical Reasoning in the NSO tests pattern detection and deduction rather than science recall. Recurring formats are number and letter series, analogies, classification, coding-decoding, direction sense, blood relations, syllogisms, dice/cube views, mirror and water images, and Venn diagrams.
Core rules
- Series: test successive differences, ratios, squares/cubes, alternating sub-series, and letter-position shifts (A=1 ... Z=26).
- Coding: write the alphabet with positions; check shift, reversal, and position-sum patterns before choosing.
- Direction: draw a compass; net displacement is the straight line from start to finish. Left/right changes with the direction a person faces.
- Blood relations: use a family tree; do not assign gender from a role word alone.
- Syllogism: a conclusion is valid only if it holds in every Venn arrangement allowed by the premises.
- Dice: opposite faces cannot be adjacent; for a standard die, opposite faces sum to 7.
Worked example
If SOUTH is coded as TPVUI, how is NORTH coded?
Compare letters: S->T, O->P, U->V, T->U, H->I. Each letter moves one step forward. Apply the same shift: N->O, O->P, R->S, T->U, H->I. Answer: OPSUI.
Mark-losing traps
Assuming "All A are B" reverses to "All B are A"; confusing "some" with "all" and forcing a conclusion that is only possible, not certain; reversing left and right in direction questions; treating a mirror image as a rotation; choosing a dice face that is adjacent to a stated face.