Classification

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Classification — Key Facts for SSC CGL • Classification means identifying the odd one out from a given group of items. The items can be numbers, words, letters, figures, or meaningful groups. • Types of Classification:

1. Number Classification: Find the number that doesn’t belong — based on prime/composite, even/odd, square/cube, divisibility, or place-value properties.
2. Word Classification: Find the odd word out — based on gender, number, synonym/antonym, category, or function.
3. Letter Classification: Odd letter out — based on alphabetical position, vowel/consonant, mirror-image position, or positional value.
4. Figure Classification: Odd figure out of five figures — based on number of sides, shading pattern, symmetry, enclosed region, or rotation. • The odd one can be identified by finding the common property shared by four items. • Digit-sum method: For number classification, add digits repeatedly to find a common property.

⚡ Exam Tip: If you’re stuck between two options, test each against the others individually. The item that fails the property test most consistently is likely the answer. In number classification, always check: prime/composite, odd/even, perfect square/cube, and digit-sum first.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Classification — SSC CGL Study Guide

Core Concept: Classification is a deductive reasoning topic where you must identify the unique property that four out of five items share, then isolate the one that does not share it. This tests your ability to spot patterns and categorise information quickly — a skill essential for SSC CGL Tier-I (Reasoning).

Common Classification Categories:

Category	What to Check
Numbers	Prime/composite, odd/even, square/cube, divisibility by 3/5/7
Words	Masculine/feminine, singular/plural, synonym/antonym, living/non-living
Letters	Vowel/consonant, alphabetical position, mirror position
Figures	Number of sides, shaded/unshaded ratio, symmetry, rotation

Worked Example 1 (Number Classification): Find the odd one out: 12, 18, 27, 36, 42

• 12: divisible by 2, 3, 4, 6
• 18: divisible by 2, 3, 6, 9
• 27: divisible by 3, 9 (only 3³)
• 36: divisible by 2, 3, 4, 6, 9, 12
• 42: divisible by 2, 3, 6, 7, 14 → 27 is the odd one because it is the only perfect cube (3³). All others are composite with more than one prime factor.

Worked Example 2 (Word Classification): Find the odd word: Mango, Apple, Carrot, Orange, Banana

• Mango, Apple, Orange, Banana → Fruits (edible sweet)
• Carrot → Vegetable (edible root) → Carrot is the odd one out (different botanical category).

Worked Example 3 (Letter Classification): Find the odd letter pair: (AB, CD, EF, GH, IJ)

• All pairs are consecutive consonants: A-B, C-D, E-F, G-H, I-J → But IJ is the odd one because I and J are vowels in some Indian classification contexts (actually I is a vowel). In standard SSC CGL classification, check for consecutive alphabetical position and alphabetical gap.

Common Student Mistakes: Overlooking that words might have multiple valid classifications (e.g., “goat” and “cow” are both animals, but “goat” is also a word with only one vowel sound). Always pick the most specific/common classification. Misinterpreting figure-based questions where rotation vs reflection is confused.

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Classification — Comprehensive SSC CGL Notes

Theoretical Foundation: Classification questions are a staple of SSC CGL Tier-I Reasoning (General Intelligence & Reasoning). They appeared in every shift of CGL 2023 Tier-I — typically 2-3 questions per exam. The underlying skill assessed is pattern recognition and logical grouping, which is foundational to administrative work.

Advanced Classification Strategies:

1. Digit Sum / Digital Root: For large numbers, compute digit sum (add digits until single digit). Numbers with the same digit sum may form a group; the one with a different sum is odd.

   • Example: 14 (→5), 23 (→5), 32 (→5), 41 (→5), 55 (→10→1) → 55 is odd

2. Roman Numeral Values: Convert numbers to Roman numerals and classify:

   • I(1), V(5), X(10), L(50), C(100), D(500), M(1000)
   • Group by number of letters in Roman representation

3. Position in Alphabet: Assign A=1, B=2…Z=26. Classify by sum, difference, or product of positions.

   • Example: ACE (1+3+5=9), BDF (2+4+6=12), CEG (3+5+7=15), DHL (8+12+9=29), EJM (5+10+13=28) — grouping by odd/even sum

4. Figure Classification — Venn Diagram Approach: For complex figures, check:

   • Number of distinct shapes enclosed
   • Number of line segments / curves
   • Presence of shading (solid, hatched, empty)
   • Rotation symmetry order
   • Interior/exterior points

Example — Figure Classification (Advanced): Given 5 figures each containing a quadrilateral: triangle only, square only, rectangle only, rhombus only, parallelogram only. The odd one depends on number of equal sides. If four have two pairs of equal sides and one does not → find the outlier.

PYQ Analysis (SSC CGL 2019-2023):

• 2023 Tier-I: 2-3 classification questions, mostly number and word based
• 2022 Tier-I: Figure classification appeared in 2nd shift with rotation symmetry
• Most difficult: Letter classification involving positional value (e.g., difference between alphabetical positions follows a pattern)
• Most common trap: A word that belongs to two categories simultaneously — always pick the most specific category that groups exactly 4 items

Practice Strategy: Build speed by timing yourself — target 30 seconds per question. Create your own classification sets from number series and word groups to internalise the patterns. Focus especially on figure classification (visual puzzles) which require spatial reasoning.

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