Relationships and ordering — SSC CGL Reasoning Notes

Concepts and rules

Blood-relation questions describe people through chains like 'my father's only son'. Your job is to reduce the chain to one standard relation.

Tree notation: write each generation on its own row, grandparents on top. Mark males with + (or a square) and females with − (or a circle), join spouses with =, siblings with a horizontal line, and parent to child with a vertical line.

Father's side: father's father = grandfather (paternal); father's brother = paternal uncle (chacha or tau); father's sister = paternal aunt (bua); their children are cousins.

Mother's side: mother's father = grandfather (maternal, nana); mother's brother = maternal uncle (mama); mother's sister = maternal aunt (mausi).

Next generation: brother's son or daughter = nephew or niece (bhatija, bhatiji); sister's son or daughter = nephew or niece (bhanja, bhanji).

In-laws: spouse's father or mother = father-in-law or mother-in-law; son's wife = daughter-in-law; daughter's husband = son-in-law; spouse's brother or sister's husband = brother-in-law; spouse's sister or brother's wife = sister-in-law.

Key reductions: my father's only son = me (if I am male); my mother's only daughter = me (if I am female); the only son of my father's father = my father; my father's wife = my mother.

Gender is known only from a gendered word (son, sister, husband) or a gender clue. A name alone is not proof in coded questions, and if a person's gender is not fixed, a relation like uncle or aunt cannot be fixed either.

Coded relations: symbols such as A + B (A is the mother of B) are decoded pair by pair from left to right, drawing each link on the tree.

Standard assumptions: siblings share both parents, a child of a married person is the child of the couple, and nobody is described twice under different names unless the question says so.

Method and shortcuts

Step 1: Identify the speaker (the 'my' person) and the target (the 'he', 'she', or the person pointed at).

Step 2: Start from the speaker and resolve the chain one link at a time: 'my father's father's only son' → 'my grandfather's only son' → 'my father'.

Step 3: Place the target on the tree and read the relation, checking generation (same row, one up, one down) and side (father's or mother's).

Step 4: For 'which expression shows that …' questions, draw each option separately and reject it at the first link that breaks gender or side.

Shortcut: the generation gap tells you the family of answers: 0 rows → sibling, cousin, spouse or sibling-in-law; 1 row → parent, uncle, aunt, nephew, niece or in-law; 2 rows → grandparent or grandchild.

Example 1: pointing to a person

Question: Pointing to a man, Ravi said, 'He is the son of the only son of my father's father.' How is the man related to Ravi?

Solution: My father's father = my grandfather. His only son = my father. The son of my father is either me or my brother; the speaker is pointing at another man, so he is Ravi's brother.

Answer: Brother.

Example 2: a short chain

Question: A is B's sister. C is B's mother. D is C's father. How is A related to D?

Solution: A and B have the same mother C, so C is A's mother. D is C's father, so D is A's maternal grandfather. A is female.

Answer: A is D's granddaughter.

Example 3: introducing a person

Question: Introducing a woman, Suresh said, 'Her mother is the only daughter of my mother.' How is the woman related to Suresh?

Solution: The only daughter of Suresh's mother is Suresh's sister (Suresh is male, so he is not that daughter). The woman's mother is Suresh's sister, so the woman is his sister's daughter.

Answer: Niece (bhanji).

Example 4: coded relations

Question: P × Q means P is the brother of Q; P + Q means P is the mother of Q; P ÷ Q means P is the father of Q; P − Q means P is the sister of Q. In A + B ÷ C − D, how is A related to D? (a) Mother (b) Aunt (c) Grandmother (d) Sister-in-law

Solution: A + B: A is B's mother. B ÷ C: B is C's father, so B is male. C − D: C is D's sister, so D is also B's child. A is the mother of D's father.

Answer: (c) Grandmother (paternal).

Example 5: a family puzzle

Question: A family of 6 (Ramesh, Sita, Mohan, Geeta, Ravi, Neha) has 3 generations and exactly 2 married couples. Ravi is the grandson of Sita. Neha is the sister of Ravi. Geeta is the daughter-in-law of Ramesh. Ramesh is the husband of Sita. How is Geeta related to Neha? (a) Aunt (b) Mother (c) Grandmother (d) Sister-in-law

Solution: Ramesh = Sita is one couple (top row). Geeta is Ramesh's daughter-in-law, so her husband is a son of Ramesh and Sita; that son cannot be Ravi, because Ravi is Sita's grandson. The only person left who can be that son is Mohan, so Mohan = Geeta is the second couple.

Ravi, Sita's grandson, must be a child of her child Mohan, and therefore of the couple Mohan and Geeta. Neha is Ravi's sister, so Geeta is Neha's mother.

Answer: (b) Mother.

Example 6: choosing the right expression

Question: A + B means A is the father of B; A − B means A is the wife of B; A × B means A is the brother of B; A ÷ B means A is the daughter of B. Which expression means M is the maternal uncle of N? (a) M × P + N (b) M + P × N (c) N ÷ P × M (d) M × P − Q + N

Solution: (a) P is N's father and M is P's brother: paternal uncle. (b) M is the father of P, and P is N's brother, so M is N's father. (c) N is P's daughter and P is M's brother, so M is P's sibling of unknown gender: paternal uncle or aunt.

(d) M is P's brother; P is Q's wife; Q is N's father. So P is N's mother and M, a male, is the mother's brother.

Answer: (d).

Common mistakes

Assuming gender from the name in coded questions. In (c) of Example 6, M's gender is never given, so the relation is not fixed.

Mixing the father's side and the mother's side. Mother's brother is mama, father's brother is chacha; both are 'uncle' in English, so read 'maternal' or 'paternal' carefully.

Forgetting that 'my father's only son' can be the speaker. If the speaker is male, it is the speaker himself.

Reading a chain from the wrong end. Start from 'my' and move outward, one link at a time.

Skipping the tree in puzzles. With 6 people and 3 generations, a quick tree prevents most errors.

Practice questions

Q1. Pointing to a photograph of a man, Meena said, 'He is the only son of my mother's father.' How is the man related to Meena? (a) Father (b) Brother (c) Maternal uncle (d) Grandfather

Q2. A # B means A is the wife of B; A @ B means A is the son of B; A & B means A is the brother of B. In P @ Q # R & S, how is P related to S? (a) Son (b) Nephew (c) Brother (d) Cousin

Q3. Pointing to a woman, Rahul said, 'Her mother's husband's only sister is my mother.' How is the woman related to Rahul? (a) Cousin (b) Sister (c) Niece (d) Aunt

Answers

Q1. (c) My mother's father is my maternal grandfather; his only son is my mother's brother, the maternal uncle.

Q2. (b) P is Q's son; Q is R's wife, so P is R's son; R is S's brother, so S is R's sibling and P, a male, is S's nephew.

Q3. (a) Her mother's husband is her father; his only sister is her paternal aunt, who is Rahul's mother. So the woman is the daughter of Rahul's mother's brother: a cousin.

Quick revision

Rows = generations; mark gender on every person; spouses with =.

Resolve from 'my' outward; 'only son of my father' may be the speaker.

Mother's brother = mama (maternal uncle); father's sister = bua (paternal aunt).

If a gender is never stated, uncle or aunt cannot be decided.

Concepts and rules

Position formula: if a person is Lth from the left and Rth from the right in a row, the total number in the row is L + R − 1, because the person is counted in both L and R.

The same rule holds for ranks: rank from top + rank from bottom − 1 = total, provided no two people share a rank.

Converting sides: position from right = total − position from left + 1.

People between two positions p and q (p < q, both from the same end) = q − p − 1.

Interchange: when A and B swap places, A takes B's old position exactly. A's new position from the left together with B's old position from the right gives the total.

Minimum and maximum: when only the gap between two people is known and not who is ahead, there are 2 cases (non-overlapping and overlapping). Work out both and pick the one asked for.

Comparison ordering: statements like 'A is taller than B but shorter than C' give a chain C > A > B. Merge all chains; a person's place is fixed only if every other person is known to be above or below.

Linear seating: for people facing north, their left and right match yours. For people facing south, their right is your left. 'Immediate right' means the very next seat; 'to the right' means anywhere on that side.

Method and shortcuts

Step 1: Draw the row as numbered blanks and write all positions from the same end (convert right-end positions with total − R + 1).

Step 2: In seating puzzles, place definite clues first (fixed seat, end seat, immediate neighbour), then use 'between' and 'not adjacent' clues to split cases.

Step 3: Keep every case alive on paper until a clue kills it; the answer must hold in the only surviving arrangement.

Shortcut: for an interchange question, the person who moved now sits in the other's old seat, so new L (of A) + old R (of B) − 1 = total in one line.

Shortcut: if A is L from the left and B is R from the right and L + R is more than the total, the two ranges overlap, so B stands to the left of A; this is the case that gives the smaller total in minimum questions.

Example 1: total from both ends

Question: Ravi is 12th from the left and 18th from the right in a row. How many people are in the row?

Solution: Total = 12 + 18 − 1 = 29. Ravi is counted in both numbers, so 1 is subtracted.

Answer: 29.

Example 2: converting rank

Question: In a class of 40, Neha's rank is 15th from the top. What is her rank from the bottom?

Solution: Rank from bottom = 40 − 15 + 1 = 26.

Answer: 26th.

Example 3: comparison chain

Question: A is heavier than B but lighter than C. D is heavier than C. E is lighter than B. Who is the second heaviest?

Solution: C > A > B from the first statement; D > C; B > E. Joined: D > C > A > B > E, a single complete chain, so every place is fixed.

Answer: C.

Example 4: minimum number in a queue

Question: In a queue, Amit is 9th from the front and Bina is 13th from the back. There are exactly 4 people between them. What is the minimum possible number of people in the queue? (a) 16 (b) 17 (c) 26 (d) 22

Solution: Case 1, Amit ahead of Bina: total = 9 + 4 + 13 = 26. Case 2, Bina ahead of Amit: Bina is 9 − 4 − 1 = 4th from the front and 13th from the back, so total = 4 + 13 − 1 = 16.

Answer: (a) 16.

Example 5: linear seating

Question: A, B, C, D, E and F sit in a row facing north. C is 3rd from the left end. A sits to the immediate right of C. Exactly 1 person sits between B and A. E sits at an end but not next to A. Neither B nor F sits at an end. D sits somewhere to the right of F. Who sits 2nd from the right end? (a) A (b) D (c) E (d) F

Solution: Seats 1 to 6 from the left: C = 3, A = 4. B is 2 seats from A: seat 2 or 6; seat 6 is an end, so B = 2. F is not at an end, so F = 5 (seats 1 and 6 are ends). D and E take seats 1 and 6; D is right of F, so D = 6 and E = 1.

Order from the left: E B C A F D. Check: E is at an end and not next to A. Second from the right is F.

Answer: (d) F.

Example 6: interchange and people between

Question: In a row of boys, Raj is 7th from the left and Vikas is 12th from the right. When they interchange positions, Raj becomes 22nd from the left. How many boys are between Raj and Vikas? (a) 13 (b) 15 (c) 14 (d) 16

Solution: After the swap Raj is in Vikas's old seat, which is 22nd from the left and 12th from the right, so total = 22 + 12 − 1 = 33. Originally Raj is at 7 and Vikas at 22 from the left, so between them = 22 − 7 − 1 = 14.

Answer: (c) 14.

Common mistakes

Adding L and R without subtracting 1. The person is counted twice.

Subtracting positions from different ends. Convert both to the same end before finding the gap.

Using q − p for the people between. The correct count is q − p − 1.

Taking only the non-overlapping case. When the question asks for the minimum, the overlapping case usually gives it.

In seating, treating 'to the right' as 'immediately to the right', or forgetting that south-facing people have left and right reversed.

Practice questions

Q1. Sunil ranks 9th from the top and 32nd from the bottom in his class. How many students are in the class? (a) 41 (b) 40 (c) 39 (d) 42

Q2. Q is older than R but younger than T. P is older than T. S is the youngest of the five. Who is in the middle by age? (a) T (b) R (c) Q (d) P

Q3. In a row of 45 children, Asha is 18th from the left and Bela is 20th from the right. How many children are between them? (a) 8 (b) 6 (c) 9 (d) 7

Answers

Q1. (b) 9 + 32 − 1 = 40.

Q2. (c) P > T > Q > R, and S is below all: P, T, Q, R, S. The 3rd is Q.

Q3. (d) Bela from the left = 45 − 20 + 1 = 26. Between = 26 − 18 − 1 = 7.

Quick revision

Total = L + R − 1; other end = total − position + 1; between = q − p − 1.

Interchange: new position of A = old position of B.

Unknown order with a fixed gap: work out both cases; overlap gives the minimum.

Seating: fixed clues first, then split cases; north-facing left = your left.