SSC MTS · Bite-size lessons

Odd One Out

About 6 min · Reasoning Ability and Problem Solving · English

Time worked out from the lesson's 414 words at 150 words a minute, plus a minute for each question.

Odd One Out (also called Classification) is a topic in the SSC MTS Reasoning section. The task is simple: given a group of 4–5 items (words, numbers, letter clusters, or figures), identify the one that does not belong. The challenge lies in spotting the hidden pattern or common property shared by most items while one deviates.

Key ideas

• Common property rule: Three or four items share a defining characteristic (mathematical, logical, categorical, or visual); one item lacks it.
• Number-based classification: Look for patterns like all even except one odd, all primes except one composite, all multiples of a number, or digit-sum properties.
• Letter-cluster classification: Check vowel/consonant count, positional values (A=1, B=2…), number of letters, alphabetical gaps, or reverse-alphabet coding.
• Word-meaning classification: Items belong to a semantic group (fruits, metals, rivers, professions); the odd one belongs to a different category or violates a sub-rule (e.g., all Indian cities except one foreign).
• Figure-based classification: Non-verbal questions test shape properties—number of sides, open vs. closed figures, symmetry, shading, rotation direction, or number of inner elements.

Watch out for

• Focusing on surface similarities: Students pick an answer based on superficial resemblance (e.g., all start with the same letter) and miss the deeper pattern (e.g., one word is an adjective, others are nouns). Fix: Always verify the rule applies to all other options before finalizing.
• Overlooking number properties: Assuming 1 is prime (it's not) or 2 is not prime (it is the only even prime). Fix: Memorize prime, square, and cube lists up to 30–40.
• Ignoring letter position values: In letter-cluster problems, students skip checking positional sums or products. Fix: For clusters like "ABC, DEF, GHJ", compute A+B+C = 6, D+E+F = 15, G+H+J = 25; spot the pattern or deviation.

Quick reference

• Number classification: Check prime/composite, even/odd, perfect square/cube, divisibility, or digit-sum patterns.
• Letter-cluster classification: Examine vowel count, position values (sum/product), alphabetical order (ascending/descending/alternating), or letter gaps.
• Word classification: Group by category (places, animals, professions) or sub-properties (gender, nationality, living/non-living).
• Figure classification: Compare number of sides, symmetry, open/closed, inner elements, shading, or rotation direction.
• Elimination hack: If stuck, compare option A with B, C, D; then B with C, D; the one that differs most consistently is the odd one out.

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

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