Direction before labels: build the coded statement
Some questions turn the code around: they give a relation and ask which expression states it. In this lesson you plan the route first (who is above whom, and through whom), write each step as a sentence, and only then pick the symbols. Then you read your expression back to check it.
Guess first
In a code, A @ B means "A is the father of B", A # B means "A is the mother of B", A % B means "A is the brother of B" and A & B means "A is the sister of B". Which expression means "P is the maternal uncle of Q"?
Show answer
Correct answer: A
Read each option back. P % M # Q: P is M's brother, and M is Q's mother. So P is the brother of Q's mother: Q's maternal uncle.
Option B: Q % M # P says Q is the brother of P's mother: Q is P's maternal uncle. The statement is turned around.
Option C: M @ Q makes M Q's father, so P would be Q's paternal uncle. The step from M to Q needs #.
Option D: M & Q makes M Q's sister, so P would be Q's brother. The step from M to Q needs #, not &.
Hint: Decode each option as sentences and name what it says.
All four look alike; only reading them back tells them apart. Building the expression yourself first makes that check quick.
Plan the route, then pick the symbols
Building a coded statement is like writing directions for a friend.
The route the path between the two people
up to a parent, down to a child, or across to a brother or sister
One turn one fact
"left is the ... of right"
Street names the symbols
chosen from the key last
Checking the directions reading back
decode your expression before you choose
This lesson uses this key:
| Symbol | Meaning |
|---|---|
| A @ B | A is the father of B |
| A # B | A is the mother of B |
| A % B | A is the brother of B |
| A & B | A is the sister of B |
In this key every parent symbol points down: the parent stands on the left and the child on the right. The brother and sister symbols point across.
See it: build "P is the paternal grandmother of Q"
Build the expression:
- Route: from P down to her child, who is Q's father, then down to Q.
- Sentences, left person first: "P is the mother of X", "X is the father of Q".
- Symbols: P # X and X @ Q, joined as P # X @ Q.
- Genders: P stands left of # (a mother, a woman); X stands left of @ (a father, so the route is on the father's side).
- Read back: P is X's mother and X is Q's father, so P is Q's father's mother.
flowchart TD P["P: mother of X"] --> X["X: father of Q"] X --> Q["Q"]
X is a helper name: the relation never mentions him, but the route needs a person in the middle. Exam options use helper names the same way.
Try it on paper. Write the route for "R is the maternal grandmother of S" as two sentences, then as an expression in this key.
Find the rule
Using this lesson's key, which expression means "K is the son of L"?
Show answer
Correct answer: A
L @ K: L is K's father. K % M: K is M's brother, so K is a man. A man who is L's child is L's son.
Option B: K & M makes K a sister, so K would be L's daughter.
Option C: K @ L makes K the father of L: the statement is turned around, and L would be K's son.
Option D: L # K makes L K's mother, but K's gender is never given: K could be a daughter.
Hint: "Son" needs two things: K below L, and K a man. Which option gives both?
Using this lesson's key, which expression means "X is the maternal grandfather of Y"?
Show answer
Correct answer: A
X @ M: X is M's father. M # Y: M is Y's mother. So X is the father of Y's mother: Y's maternal grandfather.
Option B: M @ Y makes M Y's father, so X would be the paternal grandfather.
Option C: This says Y is X's maternal grandfather: the statement is turned around.
Option D: X # M makes X a mother, so X would be the maternal grandmother.
Hint: Route first: through which parent of Y does the line go?
Name the rule
Route, sentences, symbols, check.
- Plan the route from the first person to the second: up, down or across, and through whom.
- Write each step as "left is the ... of right", with the parent on the left of a parent symbol.
- Every gender the relation needs must come from a symbol that has that person on its left.
- Read your expression back as sentences before you choose.
Building an expression goes wrong in only a few ways: a step the wrong way round, a wrong symbol, or a gender left open. Reading your own expression back as sentences catches all of them in a few seconds.
Worked, half-done, solo
Question
Using this lesson's key, build an expression that means "A is B's nephew, the son of B's sister", where B is a man.
Solution
- Plan the route
From B across to his sister S, then down to her son A.
- Write the sentences
"B is the brother of S", "S is the mother of A", and A must be a man.
- Pick the symbols
B % S, then S # A. For A's gender add a helper: "A is the brother of C", A % C.
- Join and read back
B % S # A % C: B is S's brother, S is A's mother, and A is C's brother, a man. So A is the son of B's sister.
Answer: B % S # A % C.
Watch out: B % S # A alone leaves A's gender open: A could be B's niece.
Now finish one that is half done.
Using this lesson's key, which expression means "P is the paternal aunt of Q"? Route: from Q up to Q's father F, then across to F's sister P. Sentences: "P is the sister of F", "F is the father of Q". So the expression is ...
Show answer
Correct answer: A
P & F: P is F's sister. F @ Q: F is Q's father. So P is the sister of Q's father: Q's paternal aunt, बुआ.
Option B: F # Q makes F Q's mother, so P would be Q's maternal aunt (मौसी).
Option C: P % F makes P a brother, so P would be Q's paternal uncle.
Option D: This says Q is P's paternal aunt: the statement is turned around.
Hint: Translate the two sentences one symbol at a time.
And one on your own.
Using this lesson's key, which expression means "M is the granddaughter of N, his son's daughter"?
Show answer
Correct answer: A
N @ X: N is X's father. X @ M: X is M's father, so the route goes through N's son. M & Y: M is Y's sister, a woman. So M is N's son's daughter.
Option B: X # M makes X a mother, so M would be N's daughter's daughter.
Option C: M % Y makes M a brother: N's grandson.
Option D: Nothing gives M's gender, so M could be a grandson.
Hint: Check three things: N above X, X a man, M a woman.
The traps
- A parent symbol pointing up: in A @ B the father is A, so the upper person goes on the left.
- A needed gender left open: "son", "granddaughter" or "aunt" need that person on the left of a symbol that gives the gender.
- A wrong symbol for one step: sister where mother was needed changes the whole relation.
- The statement turned around: Q % M # P says Q is P's uncle, not the other way.
- No reading back: decode the expression you chose before you mark it.
Ravi wanted "X is the maternal grandfather of Z" in this lesson's key and wrote X @ Y @ Z. What went wrong?
Show answer
Correct answer: A
X @ Y @ Z reads: X is Y's father, Y is Z's father. That makes X Z's paternal grandfather. For the maternal grandfather, Y must be Z's mother: X @ Y # Z.
Option B: X is still above Z in his expression; only the side is wrong.
Option C: The expression has two generations, as the relation needs.
Option D: The second @ puts the route through Z's father.
Hint: Read his expression back and name what it says.
Mixed check
Using this lesson's key, if P & Q @ R, how is P related to R?
Show answer
Correct answer: A
P & Q: P is Q's sister. Q @ R: Q is R's father. So P is the sister of R's father: R's paternal aunt, बुआ.
Option B: The link runs through R's father Q, so the aunt is on the father's side.
Option C: P is Q's sister. The question asks about R, one rung below Q.
Option D: This reads Q @ R backwards, as "R is Q's father". Then P would be R's daughter.
Hint: Lesson 9: decode both pairs from the left, then climb from R.
Rohit and Kavya are husband and wife. Sneha is Rohit's sister. How is Kavya related to Sneha?
Show answer
Correct answer: A
From Sneha: her brother Rohit, and his wife Kavya. Kavya is Sneha's brother's wife: her sister-in-law, भाभी.
Option B: Husband's sister (ननद) is Sneha as seen from Kavya: the reverse question.
Option C: Kavya is Rohit's wife. The question asks about Sneha.
Option D: Kavya joined the family by marrying Rohit; she is not Sneha's sister.
Hint: Lesson 8: cross the marriage last, from Sneha's side.
Quick reference
Building a coded statement
- Route
- up, down or across, and through whom paternal grandmother: down to Q's father, then down to Q
- Sentences
- left is the ... of right P is the mother of X; X is the father of Q
- Symbols
- the parent on the left of a parent symbol P # X @ Q
- Genders
- each needed gender from a symbol with that person on its left son of L: L @ K % M
- Check
- read the expression back turned around, wrong symbol, gender left open
Why it works: an expression is a list of one-step facts. Plan the steps first, and the symbols only translate them.
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