Reasoning — DSSSB TGT Section A (20 marks)
Method + one worked example per topic. Then trap patterns.
1. Analogy
Method: Find relation in the given pair → apply same relation to options. Relations: synonym, antonym, part–whole, tool–use, cause–effect, degree, category, function, word↔code pattern.
Example: Book : Reading :: Fork : ?
→ Book is used for reading; Fork is used for Eating.
Answer idea: Eating (not “Food” if relation is action).
2. Series (Number / Letter)
Number series
Method: Check +/−, ×/÷, squares/cubes, prime gaps, alternate series, two interleaved series.
Example: 2, 6, 12, 20, 30, ?
Diffs: +4, +6, +8, +10 → next +12 → 42.
Letter series
Method: Position in alphabet (A=1…Z=26); skip pattern; reverse; +n/−n; vowels/consonants.
Example: A, C, F, J, O, ?
Gaps: +2, +3, +4, +5 → next +6 → O+6 = U.
3. Coding–Decoding
Method: Map letter→letter (shift, reverse, opposite A↔Z), word→symbol, or letter position sum. Check first/last letters separately; check if vowels treated differently.
Example: If CAT = 24 (C=3, A=1, T=20 → 3+1+20), then DOG = 4+15+7 = 26.
Shift example: If APPLE → BUQQF (+1 each), then BALL → CBMM.
4. Blood Relation
Method: Draw a quick family tree. Generations as levels; male/female symbols. Convert statements one by one. Prefer “X is mother of Y” style decoding over memorising long chains.
Example: A is B’s brother. C is A’s mother. D is C’s father. How is B related to D?
→ D → C → A/B. B is grandchild of D (grandson/granddaughter as per gender if given).
5. Direction Sense
Method: Sketch N↑ S↓ E→ W←. Track facing after each turn. For shortest path: Pythagoras or net N–S and E–W displacement.
Example: A walks 5 km East, then 3 km North, then 5 km West. How far from start?
Net: 3 km North → 3 km.
6. Seating Arrangement
Linear
- Note facing North/South (left–right reverse if facing South).
- “A sits second to the left of B” ≠ “A is second left from B” confusion — read carefully.
- Place fixed person first; then neighbours; leave gaps for unknowns.
Circular
- Facing centre: left = clockwise, right = anticlockwise (standard exam convention — confirm with options).
- Facing outward: left/right reverse vs centre-facing.
- Equal spacing assumed unless said otherwise.
- “Immediate neighbours” = adjacent seats.
Tip: Draw circle with seats; mark facing with arrows; place one person and rotate if stuck.
7. Syllogism (Venn method)
Method: Draw Venn for given statements only. Conclusions must be definitely true. “Possibility” conclusions: true if not ruled out.
Standard forms:
- All A are B
- Some A are B
- No A is B
- Some A are not B
Example:
Statements: All dogs are animals. Some animals are pets.
Conclusion: Some dogs are pets → Does not follow (not definite).
Quick rules:
- All + All → All (transitive if aligned).
- All + Some → Some (careful with direction).
- No + All → No/Some not (standard conversions).
8. Statement–Conclusion
Method: Accept statement as true. Conclusion follows only if it must be true — not assumed knowledge, not “may be”. Watch extreme words (all, only, always, never).
Example:
Statement: “Company X reduced staff by 10% this year.”
Conclusion 1: Profits rose. → Not follow.
Conclusion 2: Staff count is lower than last year (if no other change stated carefully) → usually follow only if “net reduction” is clear.
Prefer: if conclusion adds new cause/motive → reject.
9. Venn Diagram
Method: Choose diagram that correctly shows overlap/disjoint/subset among groups (e.g., Teachers, Graduates, Women).
Example: Which Venn shows relation of Mothers, Women, Aunts?
→ Mothers ⊂ Women; Aunts ⊂ Women; Mothers and Aunts may overlap → two overlapping circles inside Women, or Mothers/Aunts overlapping within Women circle.
Trap Patterns (high-frequency)
| Trap | What goes wrong | Fix |
|---|---|---|
| Analogy “near miss” | Synonym vs function confused | State relation in one word first |
| Series alternate | Treating as one series | Split odd/even positions |
| Coding reverse+shift | Only applying shift | Check last letter / reverse of word |
| Blood “only child” | Assuming gender | Don’t invent gender |
| Direction facing | Turning without updating face | Mark facing after every turn |
| Linear left/right | Ignoring facing direction | Redraw for South-facing |
| Circular facing out | Using centre-facing left/right | Flip L/R |
| Syllogism “some” | Treating some as all | Some ≠ all; some can be all in possibility only |
| Possibility Q | Rejecting valid possibility | Ask: is it impossible? If no → possible |
| Statement–conclusion | Bringing outside knowledge | Stick to given text |
| Venn options | Looking similar | Check subset vs intersection carefully |
| Negative conclusions | Misreading “not” | Underline negatives |
Exam habit: 20 Q in ~15–18 min. Skip lengthy seating if stuck; return later.