In a certain code language, ‘A + B’ means ‘A is the mother of B’; ‘A − B’ means ‘A is the brother of B’; ‘A × B’ means ‘A is the wife of B’ and ‘A ÷ B’ means ‘A is the father of B’. Based on the above, how is 5 related to 3 if ‘5 − 2 × 4 ÷ 3’?
- (a)Father’s brother
- (b)Father’s sister
- (c)Mother’s sister
- (d)Mother’s brother
Answer
Why
Correct — D. Read the string strictly left to right, one symbol at a time.
Rule: + is mother of, - is brother of, x is wife of, / is father of.
5 - 2: 5 is the brother of 2.
2 x 4: 2 is the wife of 4.
4 / 3: 4 is the father of 3.
4 is 3's father and 2 is 4's wife, so 2 is 3's mother.
5 is 2's brother, which makes 5 the mother's brother of 3 — option (d).
Why the others are wrong
- (a)Father’s brother — For this, 5 would have to be the brother of 4, the father. The string attaches 5 to 2, and 2 is the wife in the pair, not the father.
- (b)Father’s sister — 'A - B' means A is the brother of B, so 5 is male and cannot be anyone's sister. The link also runs through the mother, not the father.
- (c)Mother’s sister — The side of the family is right — 5 does reach 3 through the mother 2 — but the symbol between 5 and 2 is brother, not sister.
Concept
A coded blood relation gives you a symbol table and a string, and the entire task is to read the string left to right, treating each symbol as a statement about the pair on either side of it.
Do not apply BODMAS. The 'x' here is not multiplication and carries no precedence — the expression is a sentence, not a calculation.
Then build the family. The wife of a child's father is that child's mother, so her brother is the child's maternal uncle.
The symbols also fix gender, and that settles half the options before any diagram is drawn.
'-' makes 5 male and 'x' makes 2 female, so neither 'Father's sister' nor 'Mother's sister' can survive.
Key facts
- In this code '+' is mother of, '-' is brother of, 'x' is wife of and '/' is father of.
- Code strings of this type are read left to right, with no operator precedence.
- The wife of a person's father is that person's mother, so her brother is the maternal uncle.
Study next
Common traps
- Applying BODMAS and evaluating 'x' before '-'.
- Missing that '-' fixes 5 as male, which alone rules out both sister options.
- Describing the link from 5's side when the question asks how 5 is related to 3.
The symbol table is printed with the question, so read it rather than recall it - though it is not always a fresh one. This exact table (+ mother, − brother, × wife, ÷ father) is reprinted at 12 Sep 2024, 09:00, Reasoning Q.23 and at 18 Sep 2024, 12:30, Reasoning Q.1.
This shift also codes words rather than relations — also 10 Sep 2024, 16:00, Reasoning Q.10.
Related PYQs
No directly related past PYQ was found.