LR03 — Classification — Odd One Out
🧠 AFCAT Reasoning · LR03
✈️ AFCAT Level
📌 AFCAT Pattern (LR03): Classification (Odd One Out) tests your ability to find the element that does NOT share the common property of the remaining three. 2–3 questions per paper. The common trap: surface similarity. Always find the DEEPEST common property shared by three items and identify what the fourth lacks.
PART A — WORD CLASSIFICATION
1. Category-Based Classification
How to Approach
- List all four items
- Find what THREE of them share (category, property, function, group)
- The FOURTH is the odd one
- Beware: sometimes the obvious grouping is a trap — look deeper
Common Categories in AFCAT
- Military ranks: General, Admiral, Air Marshal, Corporal (lowest rank — others are senior)
- Aircraft types: Fighter, Bomber, Transport, Submarine (naval, not air)
- Weapons: Missile, Torpedo, Shell, Radar (detection device, not a weapon)
- Countries: USA, Russia, France, Japan (if context = P5 UN members)
Worked Example 1
Which is odd: Eagle, Hawk, Osprey, Penguin
Eagle, Hawk, Osprey = birds of prey (raptors) that fly and hunt. Penguin = bird that cannot fly and does not hunt like a raptor. Answer: Penguin
Trap: All four are birds. The deeper property = birds of prey / flying hunters.
Worked Example 2 — Military Context
Which is odd: INS Vikrant, INS Imphal, INS Vaghsheer, HAL Tejas
INS prefix = Indian Naval Ship (all three are naval vessels). HAL Tejas = Indian Air Force aircraft. Answer: HAL Tejas
Property: All three INS vessels are Indian Navy assets. Tejas is IAF.
2. Number Classification
3. Letter Classification
Position-Based
- BCD, EFG, HIJ, KLN → KLM should be consecutive (N breaks it)
- BDFH, ACEG, JLNP, MOQS → MOQS gaps: +2 each ✓ — same pattern; check carefully
- Vowel classification: A,E,I,O vs U (if others pattern differently)
Symmetry-Based
- Letters with vertical symmetry: A,H,I,M,O,T,U,V,W,X,Y
- Letters with horizontal symmetry: B,C,D,E,K
- Odd one: letter that breaks the symmetry class
- Example: A,H,M,S — S has no axis of symmetry
📝 AFCAT PYQClassification — AFCAT Pattern
Q1. Find the odd one: Rafale, Su-30MKI, Tejas, C-17 Globemaster (AFCAT I 2025)
- (a) Rafale
- (b) Su-30MKI
- (c) Tejas
- (d) C-17 Globemaster
Answer: (d) C-17 Globemaster
Rafale, Su-30MKI, and Tejas are all fighter/combat aircraft designed for air superiority, ground attack, and combat missions. The C-17 Globemaster is a strategic heavy transport aircraft — it carries troops, cargo, and equipment but is not a combat aircraft. This is an AFCAT-specific question combining GK with reasoning.
Q2. Which is odd: 17, 23, 37, 51? (AFCAT II 2024)
Answer: (d) 51
17, 23, 37 are all prime numbers (divisible only by 1 and themselves). 51 = 3 × 17, so it is composite. Always verify each number: 17 (prime ✓), 23 (prime ✓), 37 (prime ✓), 51 (3×17, not prime ✗). Odd = 51.
Q3. Find odd: IAF, INS, INA, ITBP (AFCAT I 2024)
- (a) IAF
- (b) INS
- (c) INA
- (d) ITBP
Answer: (b) INS
IAF = Indian Air Force; INA = Indian National Army (historical); ITBP = Indo-Tibetan Border Police — all are/were land-based/ground forces (IAF uses air but is part of tri-service). INS = Indian Naval Ship prefix — it refers to a specific ship, not a force/organisation. The others are names of armed forces or para-military organisations. INS is a prefix for a naval vessel.
⚡ Quick Reference — LR03
Strategy
- Find property THREE share — not two
- Test all options as potential odd one
- Look DEEPER than surface category
- AFCAT loves military-context classification
Number Properties
- Prime: 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47
- Perfect squares: 1,4,9,16,25,36,49,64,81,100
- Perfect cubes: 1,8,27,64,125,216
Letter Symmetry
- Vertical: A,H,I,M,O,T,U,V,W,X,Y
- Horizontal: B,C,D,E,K
- No symmetry: F,G,J,L,N,P,Q,R,S,Z
This material is for personal AFCAT exam preparation only. Unauthorised reproduction prohibited.
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