Blood Relations, Direction Sense & Coding

Syllabus Unit: Reasoning Ability

Why it matters

Chapter overview

This topic bundles three classic Reasoning puzzle types that each hinge on tracking relationships methodically on paper: blood relations (family trees from a chain of statements), direction sense (net displacement and final direction from a sequence of turns), and coding-decoding (letter or number substitution patterns) — plus ordering and ranking, which applies the same relative-position logic used in seating arrangements to a single line of rank.

Preliminary Examination Syllabus Reasoning Ability 35% weightage

Live Animation1 / 4

Grandfather's GenerationOldest generation in the tree

Father's GenerationGrandfather's only son

Speaker's GenerationSpeaker and his sister

1Blood Relations & Family Trees

Every blood-relation puzzle is a family tree in disguise — draw it with a generation-by-generation symbol system and the answer reads itself off.

Learning Objectives

Build a standard symbol system for family trees (male/female, marriage link, parent-child link).
Decode multi-step relational phrases ('mother's only brother's son') one relation at a time, in order.
Distinguish generation-shifting relations (uncle, grandfather) from same-generation relations (sibling, cousin).
Handle ambiguous gender clues by tracking both possibilities in the tree until a later statement resolves it.

Key Terms

Family Tree NotationA symbol shorthand (e.g., triangle=male, circle=female, horizontal line=marriage, vertical line=parent-child) used to sketch relations as they're read.

Generation LevelThe horizontal tier a person belongs to in the tree; siblings and cousins share a level, while parents and children sit one level apart.

Compound RelationA chained phrase like 'father's sister's husband', solved one possessive relation at a time in the order given, rather than guessed at all once.

Ambiguous Gender ClueA relation term (e.g., 'child', 'cousin', 'sibling') that doesn't specify gender, requiring both possibilities to be held in the tree until resolved.

Every blood-relation question, however convoluted the sentence, describes one small family tree. The skill is entirely mechanical: convert each relational phrase into a symbol on the tree as it's read, one step at a time, rather than trying to hold the whole chain in your head.

The notation system

Use a fixed symbol for male and a different one for female as each person is introduced.
Draw a horizontal line between two people who are married.
Draw a vertical line down from parents to each child.
Keep generations aligned on the same horizontal level as you add people.

Decoding compound relations, one step at a time

Worked example: 'She is the daughter of my grandfather's only son.' Decode right to left: 'my grandfather's only son' = my father (since the grandfather has exactly one son, and the speaker descends through him). 'The daughter of my father' = my sister.

Grandfather's only son → Father ⟹ Father's daughter → Sister

Common MistakeTrap: assuming a gender-neutral term like 'child', 'cousin', or 'sibling' refers to a specific gender before a later clue confirms it — keep both possibilities open in the tree.

Exam TipDraw the tree top to bottom by generation, and left to right within a generation, adding each new person to the diagram the moment they're introduced — never solve purely from the sentence in your head.