Logical Problems

The three sub-types you must master

• Seating arrangement: people in a row or circle with positional clues.
• Blood relations: family-tree problems coded with phrases like "the son of my father's brother".
• Direction sense: someone walks N, then E, then S; find final position or distance.

Seating arrangement: draw the table

Always sketch the configuration. For a circle of six, draw six chairs and number them 1 through 6. Translate each clue into a constraint: "A sits opposite B" means positions 1 and 4 (or 2 and 5, etc.). "C is to the immediate right of D" depends on whether the circle is facing inward or outward; read the question carefully.

Blood relations: the pointing technique

The classic clue: "Pointing to a man, Reema said, 'He is the son of my father's only sister.'" Decode step by step. Father's only sister = aunt. Aunt's son = cousin. So the man is Reema's cousin. Always parse from the inside outward and write each relation in margin shorthand: F = father, M = mother, S = son, D = daughter, B = brother, Si = sister.

Direction sense: the coordinate method

Set the start at (0, 0). North adds to y, South subtracts from y, East adds to x, West subtracts. After tracking all moves, use the Pythagorean theorem to find shortest distance. Example: a person walks 3 km north, then 4 km east. Final position is (4, 3); distance from start is the square root of (16 + 9) = 5 km.

Worked seating example

Five friends — A, B, C, D, E — sit in a row facing north. C sits to the immediate left of D. B sits at one of the ends. A is between C and E. Where does B sit?

Place A between C and E: pattern is C-A-E or E-A-C. Add "C immediate left of D": C must be followed by D. So the chain is E-A-C-D; that leaves position 1 or 5 for B. Since B sits at an end and the chain occupies positions 2 to 5, B is at position 1. Final order: B-E-A-C-D.

Time management

Logical problems are slow. Cap at 90 seconds; if you have not drawn a clean diagram in 30 seconds, you have mis-parsed a clue. Re-read the constraints from scratch rather than guessing.