Blood relations for RRB Group D

Blood relation questions describe a family in a few short sentences and ask how two people are related. The relation words are everyday ones: uncle, niece, grandson, mother-in-law. The trouble is that the sentences are chained, and one wrong step in your head gives a wrong answer that is also one of the options.

The cure is simple. Always draw a small family tree. It takes ten seconds and removes almost every mistake.

How to draw the family tree

• Put older generations higher and younger ones lower.
• Join brothers and sisters with a horizontal line.
• Join a parent and child with a vertical line.
• Join a husband and wife with a double line (=) or a small loop.
• Mark M for male or F for female, but only when a word in the question tells you.

Relation words you must know

The four question types

• Direct statements ("A is the father of B"): draw each fact as you read it.
• Pointing or introducing ("Pointing to a man, a woman says…"): start from the speaker's "my" and work outwards.
• Coded relations ("P × Q means P is the mother of Q"): turn each symbol into a sentence first, then draw.
• Family puzzles (six people, several facts): draw the full tree once and answer every question from it.

Worked examples

Example 1 (direct): Q is the son of P. R is the daughter of P. How is Q related to R?

• Q and R are both children of P, so they are siblings.
• "Son" tells us Q is male. Q is R's brother.

Example 2 (direct): X is the sister of Y. Y is the mother of Z. How is X related to Z?

• X is female ("sister"). X is the sister of Z's mother.
• X is Z's aunt (a maternal aunt).

Example 3 (pointing): Pointing to a woman, a man says, "Her mother is the only daughter of my mother." How is the woman related to the man?

• Start with "my mother": the man's mother. Her only daughter is the man's sister.
• The woman's mother is the man's sister, so the woman is his sister's daughter: his niece.

Example 4 (coded): P × Q means P is the mother of Q. P + Q means P is the brother of Q. P − Q means P is the sister of Q. P ÷ Q means P is the father of Q. What does A + B × C mean?

• A + B: A is the brother of B, so A is male.
• B × C: B is the mother of C.
• A is the brother of C's mother, so A is C's maternal uncle.

Example 5 (family puzzle): A family has six members: P, Q, R, S, T and U. P is a man married to Q, a woman. R (male) and S (female) are the son and daughter of P and Q. T is R's wife. U is the son of R and T.

The tree, top to bottom:

• Generation 1: P (M) = Q (F)
• Generation 2: R (M) = T (F), and R's sister S (F)
• Generation 3: U (M), child of R and T

Now read the answers off the tree:

• How is U related to Q? Q is the mother of U's father, so U is Q's grandson.
• How is S related to U? S is the sister of U's father, so S is U's aunt (a paternal aunt).
• How is T related to P? T is the wife of P's son, so T is P's daughter-in-law.

Common mistakes

• Solving in your head instead of sketching.
• Assuming gender from a name, or reading "A is the brother of B" as telling you B's gender. It only tells you A is male.
• Reading the relation the wrong way round. "How is A related to B?" wants A's relation to B, so start the answer from B's side: "A is B's…".
• Forgetting the in-law step. A mother's son-in-law is her daughter's husband, not her son.

Practice set

Use these codes for questions 5 and 6: P × Q means P is the mother of Q; P + Q means P is the brother of Q; P − Q means P is the sister of Q; P ÷ Q means P is the father of Q.

1. M is the brother of N. N is the son of O. How is M related to O?
2. P is the mother of Q. Q is the wife of R. How is P related to R?
3. S is the daughter of T. T is the brother of U. How is S related to U?
4. Pointing to a man, a woman says, "He is the son of my father's only son." How is the man related to the woman?
5. What does A − B × C mean?
6. What does A ÷ B + C mean?
7. K is the child of L. L is the sister of M, and M is a man. How is K related to M?
8. Introducing a boy, a girl says, "He is the son of the daughter of my father's father." How is the boy related to the girl?

Answers:

1. Son. M is male ("brother") and a sibling of N, so M is also O's child.
2. Mother-in-law. P is the mother of R's wife.
3. Niece. S is female ("daughter"), and her father T is U's brother.
4. Nephew. The speaker is a woman, so her father's only son is her brother. The man is her brother's son.
5. A is C's aunt (maternal). A is female and the sister of B, and B is C's mother.
6. A is C's father. A is the father of B, and B is C's brother, so A is the father of both.
7. Nephew or niece; the exact word cannot be determined. K is the child of M's sister, but K's gender is not given.
8. Cousin. The girl's father's father is her grandfather. His daughter is her aunt, and the aunt's son is her cousin.

What to do next

• Learn the relation-words table until you can fill it in from memory.
• Solve 10 blood relation questions a day for a week, drawing a tree for every one.
• Practise directions next, which also rewards a quick sketch, and revise coding–decoding for symbol-reading speed.