Decode, check, and know when to stop
Symbols are a compact language
About 12–15 minutes including practice. Recall: a person can be a grandmother even when the maternal or paternal branch is not known. Different missing facts cause different uncertainty.
In this lesson +, /, and ~ are relationship labels defined by each question. They are not addition, division or arithmetic precedence. Read each adjacent pair as a sentence. Always read the legend again when a new question begins.
Warm-up: X + Y means X is Y’s mother. X / Y means X is Y’s father. In A + B / C, what is A to C?
Show answer
Correct answer: C
Decode adjacent pairs: A is B’s mother; B is C’s father. A is the mother of C’s father: paternal grandmother. Symbols are relation labels, not arithmetic.
Option A: There are two parent links, not one.
Option B: The second link names C’s father.
Option C: The path is through C’s father B.
Option D: No sibling link appears.
Hint: Translate both pairs into sentences first.
Worked example: translate before solving
Here X ~ Y means X is Y’s brother, and X / Y means X is Y’s father. Decode P ~ Q / R.
- Decode P ~ Q only: P is Q’s brother. Mark P male. This first clue alone does not state Q’s gender.
- Decode Q / R only: Q is R’s father. Now Q is male, while R’s gender is unknown.
- Start at R: father Q, then Q’s brother P. P is R’s father’s brother.
- Stop before inventing age. The clues do not say whether P is older or younger than Q. “Father’s brother” is safe; choosing ताऊ versus चाचा is not justified here.
The uncertainty check
Ask two separate questions: Is the relationship known? Is the detail requested known?
For “A is B’s mother; B is C’s parent”, A is a grandmother of C. But B could be the mother or father, so the maternal/paternal branch is unknown. “Nothing can be known” would be too strong.
To disprove certainty, show two families that satisfy the clues but give different requested answers. You need not invent extra family details unrelated to the question.
Complete the method: X ~ Y means X is Y’s brother; X / Y means X is Y’s father. In P ~ Q / R, P is R’s father’s brother. Can we select “elder paternal uncle” rather than “younger paternal uncle”?
Show answer
Correct answer: D
The relation is father’s brother. Neither symbol states whether P is older or younger than Q. Do not invent the age needed for ताऊ versus चाचा.
Option A: No clue compares the brothers’ ages.
Option B: No clue compares the brothers’ ages.
Option C: The symbols encode relation and gender, not relative age.
Option D: Father’s brother is known; elder/younger is not.
Hint: Which clue supplies the age comparison?
Now practise without the safety net
Open this lesson’s separate five-question practice test. For the first attempt, do not use the worked example or hints. There is no speed target: accurate reasoning comes first. After submitting, read the explanation even if a guess happened to be correct.
Your paper error log: record the question number, your first answer, whether you were sure or guessing, and one error label: direction / gender / generation / missing fact. Write one sentence explaining the corrected path. Keep this confidence note on paper.
If a question exposed a gap, revisit only the relevant worked step, then solve it again from a blank page. A correct retry shows recovery, not the same thing as an unaided first attempt.
A two-minute return visit
Tomorrow, before reopening this lesson, draw one relationship chain from memory and explain what remains unknown. Then retry two questions you missed or guessed. If none caused difficulty, make two new examples and explain them. Review again later in the week if useful; choose a time that fits your study routine.
Ready to move on? You can explain the path without reading the solution and can name what the clues do not establish. If not, repair that one step before adding speed.
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