Logical Reasoning
Logical Reasoning checks whether you can hold a set of conditions in mind and derive only what actually follows. The recurring types are number and alphabet series, coding-decoding, blood relations, direction sense, syllogism, order and ranking, seating arrangement, inequalities, analogy and odd-one-out. Non-verbal figure series also appear, so practise spotting rotation, element addition and mirroring.
Method over memory
- Series: test differences first, then ratios, then alternating patterns, then squares and cubes.
- Coding: write the alphabet with positions 1-26 and look for fixed or shifting offsets.
- Blood relations: draw a family tree; mark gender only where the question states it.
- Syllogism: draw minimal Venn diagrams; a conclusion is valid only if it holds in every possible diagram.
- Directions: fix a compass at the start and remember that right and left are relative to the direction currently faced.
Worked example
A person walks 5 km north, turns right and walks 3 km, then turns right again and walks 5 km. How far is he from the start, and in which direction?
Set the start at (0,0). Walking north takes him to (0,5). Facing north, a right turn means east, so he reaches (3,5). Facing east, a right turn means south, so he ends at (3,0). The north and south legs cancel, leaving a displacement of 3 km due east. Answer: 3 km east.
Traps that cost marks
- Assuming a right turn always means east, ignoring the current facing direction.
- In syllogism, accepting a 'some' conclusion that is true in one diagram but not all.
- Assuming the gender of a person in a blood-relation puzzle from the name alone.
- Forgetting the reverse alphabet positions (A = 26, Z = 1) in coding questions.
- In seating arrangement, mixing left and right when some people face north and others south.