Blood Relations
Scenario
Every TCS/Infosys reasoning section throws a 'Pointing to a photo, X said...' puzzle.
Do you solve it in your head and second-guess, or in 15 seconds on paper?
Mental model
Don't track relationships in words - draw the family TREE.
Generations stack top-to-bottom; a married couple sits side by side. Once it's a diagram, the answer is just reading the path between two boxes - no working memory required.
Method
- Spot the two people and the link word (son, sister, maternal uncle, father-in-law).
- Anchor the speaker / reference person as a box; draw generations top (elder) to bottom (younger).
- Mark gender (+ for male, - for female) and couples (=), parent-child with a vertical line.
- Read the path between the two target boxes to name the relation.
Worked example
Problem: Pointing at a man, Riya says: 'He is the son of my grandfather's only son.' How is the man related to Riya?
- 'Grandfather's only son' = Riya's father (he is the single son of the grandfather).
- The man is the son of Riya's father.
- Son of Riya's father = Riya's brother.
Answer: He is Riya's brother.
Shortcuts
- Collapse 'only' phrases: 'Only son / only daughter of X' usually collapses to one known person - replace it immediately. ('My mother's only son' = me (if male) or my brother.)
Common mistakes
- Assuming gender from the name or context: 'The child of X' may have unstated gender. Only use the gender the puzzle explicitly gives - guessing flips the answer.
- Reading the chain in words instead of drawing it: Multi-hop relations like 'father-in-law of the brother of...' exceed working memory. Draw the tree and the error rate drops to near zero.
Glossary
- maternal
- Related through the mother side of the family.
- reference
- The starting person you are using to map out a relationship.
- generations
- Levels in a family tree, like grandparents, parents, and children.
Recall questions
- What is the first move on any blood-relations puzzle?
- How do you simplify 'my grandfather's only son'?
- Why is solving these in your head so error-prone?
Questions & answers
A is B's sister. C is B's mother. D is C's father. How is A related to D?
Granddaughter.
Approach: Tree: D -> C -> (A, B). A is female (sister of B) and sits two generations below D, so A is D's granddaughter.
Pointing to a woman, Karan said, 'She is the daughter of the only daughter of my mother.' How is the woman related to Karan?
Niece.
Approach: 'Only daughter of my mother' = Karan's sister. The woman is that sister's daughter = Karan's niece.