Reasoning: Series, Coding-Decoding and Logical Diagrams
The Reasoning section tests logical and analytical ability through verbal and non-verbal items: series, analogies, coding-decoding, blood relations, direction sense, syllogism, seating arrangement, classification, and figure-based questions. Most items are solvable in under a minute once the pattern is named.
Core rules
- Alphabet: A=1 to Z=26; EJOTY gives E=5, J=10, O=15, T=20, Y=25; opposite letters sum to 27 (A-Z, B-Y).
- Series: check differences, then ratios, then squares and cubes, then alternating series.
- Coding: identify whether letters shift forward or backward, reverse, or substitute; write the alphabet above the word.
- Blood relations: draw a family tree with gender symbols; expressions such as only son or only daughter are restrictive.
- Directions: sketch the axes; use Pythagoras for the shortest distance.
- Syllogism: draw minimal Venn diagrams; do not assume relations that are not stated.
Worked example
Series: 3, 8, 15, 24, ? Differences are 5, 7 and 9, increasing by 2, so the next difference is 11. 24 + 11 = 35. The pattern is n squared minus 1 (4-1, 9-1, 16-1, 25-1), confirming 35.
Traps
- Missing a negative or decreasing shift in coding.
- Treating all A are B as all B are A.
- Ignoring the starting point and facing direction in direction or rotation questions.
- Over-marking in syllogism by adding conclusions that the diagram does not force.
- Forgetting that in seating arrangements, left and right depend on the direction each person faces.