Blood relations for RRB NTPC: family trees, coded relations and practice

Blood relation questions describe a family in two or three short statements and ask how two people are related. The logic is never hard. What goes wrong is keeping four people, two generations and several genders in your head at once. So the whole method comes down to one rule: draw the family tree, every time, even for a two-line question.

In NTPC these usually appear as direct statements, coded relations (where symbols stand for "father of", "sister of" and so on) and "pointing to a photograph" puzzles. A clean diagram handles all three.

The diagram method

1. Put the oldest generation at the top and each younger generation one row lower.
2. Draw one statement at a time. Do not jump ahead.
3. Add + or − only when a relation word gives the gender.
4. Read the question direction carefully: "How is A related to B?" asks what A is to B.

Relation words you must know

"Maternal" means on the mother's side; "paternal" means on the father's side. A mother's brother is a maternal uncle.

Worked questions

Q1. P is the father of Q. Q is the sister of R. How is R related to P?

P is a parent of Q, and Q and R are siblings, so P is also R's parent. R's gender is not given anywhere. R is P's child; whether son or daughter cannot be determined.

Q2. A is the brother of B. B is the daughter of C. How is A related to C?

A and B are siblings, and C is their parent. "Brother" tells us A is male. A is C's son.

Q3. X is the mother of Y. Y is the husband of Z. How is X related to Z?

Y is Z's husband, and X is Y's mother. The mother of one's husband is one's mother-in-law. (X is female from "mother".)

Q4. K is the sister of L. L is the wife of M. How is K related to M?

L is M's wife. K is L's sister, so K is female. The sister of one's wife is one's sister-in-law.

Q5. O and P are a married couple, and P is female. N is their daughter, and M is N's son. How is P related to M?

Draw three generations: O and P at the top, N below them, M below N. P is the mother of M's mother. P is M's maternal grandmother.

Q6. Coded. P + Q means P is the father of Q. P − Q means P is the sister of Q. P × Q means P is the brother of Q. What does A + B − C mean?

• A + B: A is the father of B.
• B − C: B is the sister of C, so B and C are siblings.
• So A is the father of C as well. A + B − C means A is the father of C.

Q7. Photograph. Pointing to a photograph, a man says, "She is the daughter of my father's father's only son." How is the woman in the photograph related to the man?

• My father's father is my paternal grandfather.
• His only son must be my father.
• The daughter of my father is my sister.

When the answer is "cannot be determined"

If a question asks "how is R related to P" and R's gender is never given, "son" and "daughter" are both unsafe. Look for an option like "child" or "cannot be determined". This is not a trick; it is the question testing whether you invented a gender.

The same applies to marriages. If two people are described only as the parents of a child, the question usually means them to be a couple, but state that assumption in your working rather than adding facts the question did not give.

Common mistakes

• Assuming a gender from a name or a letter.
• Mixing up generations. A parent's sibling is one generation up; a cousin is on your own level.
• Reading the question backwards. "How is A related to B" means A's role with respect to B.
• Dropping the in-law in marriage questions. A wife's sister is a sister-in-law, not a sister.
• Solving coded relations in your head. Translate each symbol into words and draw it.

Practice set

1. A is the sister of B. B is the son of C. How is A related to C?
2. M is the father of N. N is the brother of O. How is M related to O?
3. P is the wife of Q. Q is the son of R. How is P related to R?
4. Pointing to a boy, a woman says, "He is the son of my mother's only child." How is the boy related to the woman?
5. Using the codes in Q6, what does A × B − C mean?
6. D is the brother of E. E is the mother of F. How is D related to F?
7. G is the son of H. H is the brother of J, and J is female. How is J related to G?
8. Using the codes in Q6, what does C − A + D mean?

Answers:

1. Daughter. A and B are siblings, so C is A's parent; "sister" makes A female.
2. Father. N and O are siblings, so M is O's parent; "father" makes M male.
3. Daughter-in-law. P is married to R's son; "wife" makes P female.
4. Son. Her mother's only child is the woman herself, so the boy is her son.
5. A is the brother of C. A is the brother of B, and B is the sister of C, so all three are siblings; A is male.
6. Maternal uncle. E is F's mother, and D is E's brother.
7. Paternal aunt. H is male (brother) and G's parent, so H is G's father. J is H's sister.
8. C is the paternal aunt of D. C is A's sister (female), and A is D's father.

What to do next

• Draw a tree for every one of your next 20 questions, including the easy ones.
• Mark + and − only when a relation word gives the gender. Circle any person with no gender given.
• Move on to direction and distance, the next diagram topic.
• Mix blood relations into timed sets with order and ranking.