Module 2: S4 Reasoning
Topic 3: Blood Relations & Direction Sense
1 Direction Sense: The Complete Arsenal
The Standard Compass Map
Angle between Main directions = 90°
Angle between Main & Sub = 45°
Distance Formula (Shortest Path)
When asked for the "shortest distance" or "distance from the starting point," you must form a Right-Angled Triangle and apply Pythagoras Theorem.
P = Perpendicular (Vertical Dist)
B = Base (Horizontal Dist)
(3, 4, 5) | (5, 12, 13) | (6, 8, 10) | (8, 15, 17)
Degree Rotation Hack
Do NOT draw every single turn. It wastes time and leads to overlapping messy lines.
- Sum all Clockwise (CW) turns.
- Sum all Anti-Clockwise (ACW) turns.
- Subtract the smaller from the larger.
- Turn the net difference in the direction of the larger sum from the starting face.
The Shadow Algorithm
| Time of Day | Sun Position | Shadow Falls |
|---|---|---|
| Morning (Sunrise) | EAST | WEST |
| Evening (Sunset) | WEST | EAST |
| 12:00 Noon | OVERHEAD | NO SHADOW |
Admin Context Tip: If the Principal is walking North in the morning, their shadow is to their Left (West).
2 Blood Relations: The Generation Tree
Never attempt to solve family puzzles in your head. You must translate the text into a visual Family Tree using standard logic symbols.
Standard Notation
Crucial Terminology Mapping
| Paternal | Father's side of the family. (Paternal Uncle = Father's brother). |
| Maternal | Mother's side of the family. (Maternal Aunt = Mother's sister). |
| Nephew / Niece | Nephew = Brother's or Sister's Son. Niece = Brother's or Sister's Daughter. |
| Sibling | Brother or Sister (sharing at least one parent). |
| In-Laws | Relatives through marriage (Spouse's parents/siblings). |
3 UPSC Traps & Pointing Puzzles
⚠️ The Gender Assumption Trap
Never, ever assume the gender of a person based purely on their name in a logic puzzle.
"Kiran is the child of P. P is the husband of Q."
Question: How is Kiran related to Q?
Trap Answer: Son / Daughter.
True Answer: Cannot be determined. The text does not explicitly state Kiran's gender.
The "Backwards" Technique
For questions starting with "Pointing to a photograph...", always break the sentence down backwards from the word 'MY'.
Solving Backwards:
1. "My grandfather" = The woman's grandfather.
2. "Only son of my grandfather" = The woman's Father.
3. "He is the son of [the woman's Father]" = The woman's Brother.
Answer: The man is her Brother.
4 Coded Blood Relations (High Difficulty)
Group-A exams frequently use symbols to denote relations to test calculation speed and accuracy.
| Coded Legend Provided in Exam | |
|---|---|
| A $ B | A is the Mother of B |
| A # B | A is the Father of B |
| A @ B | A is the Husband of B |
| A % B | A is the Daughter of B |
Question: In the expression P @ Q $ M # T, how is P related to T?
- P @ Q ➡ P is the Husband of Q. (P is Male 🔲, Q is Female ⭕, Married).
- Q $ M ➡ Q is the Mother of M. (M is a generation below).
- M # T ➡ M is the Father of T. (M is Male 🔲, T is a generation below M).
Conclusion: P is the husband of the mother (Q) of the father (M) of T. Therefore, P is the father of M, and M is the father of T. This makes P the Paternal Grandfather of T.