Reasoning Chapters

1. NUMBER AND LETTER SERIES2. ALPHANUMERIC SERIES3. MISSING NUMBER4. ANALOGY SIMILARTY5. CLASSIFICATION6. DIRECTION 7. BLOOD RELATION8. SEATING ARRANGEMENT9. PUZZLE10. ORDER AND RANKING11. SYLLOGISM12. CLOCK13. CALENDER14. WORD FORMATION15. DICE16. CUBE AND CUBOID17. MIRROR AND WATER IMAGE18. VENN DIAGRAM19. STATEMENT AND ASSUMPTION

Classification (Odd One Out)

Classification or "Odd One Out" questions test your ability to identify the element that doesn't belong in a group based on common features, categories, or logical relations.

What is Classification?

In classification problems, you're given a set of items (numbers, words, letters, figures), and you must find the one that doesn't fit with the rest. These questions assess your logical thinking and ability to identify patterns or anomalies.

Types of Classification Patterns:

  • Word-based classification (based on meaning, category)
  • Number-based classification (based on mathematical properties)
  • Letter-based classification (alphabetical patterns)
  • General knowledge-based classification

Example:

Q: Apple, Banana, Carrot, Mango
Ans: Carrot (It is a vegetable, others are fruits)

30+ Previous Year Questions with Solutions

  1. SSC CHSL 2021: Dog, Cat, Cow, Snake
    Answer: Snake (Others are mammals)
  2. RRB NTPC 2019: 21, 25, 29, 34
    Answer: 34 (Others are prime numbers)
  3. SSC CGL 2018: Pen, Pencil, Eraser, Paper
    Answer: Paper (Others are used to write)
  4. HSSC JE 2019: Oxygen, Hydrogen, Iron, Nitrogen
    Answer: Iron (It is a metal, others are gases)
  5. SSC MTS 2021: Triangle, Square, Circle, Rectangle
    Answer: Circle (No sides, others have sides)
  6. SSC GD 2020: Rose, Lotus, Marigold, Mango
    Answer: Mango (It is a fruit, others are flowers)
  7. RRB Group D 2018: 64, 125, 216, 343, 400
    Answer: 400 (Not a cube number)
  8. SSC CGL 2020: Monday, Tuesday, Friday, January
    Answer: January (It's a month, others are weekdays)
  9. SSC JE 2018: A, E, I, O, M
    Answer: M (Not a vowel)
  10. SSC CHSL 2017: Car, Bus, Train, Aeroplane
    Answer: Car (It does not carry many passengers)
  11. RRB ALP 2017: Copper, Gold, Iron, Diamond
    Answer: Diamond (It is a non-metal)
  12. HSSC Clerk 2016: 11, 13, 17, 22
    Answer: 22 (Not a prime number)
  13. SSC MTS 2016: Sparrow, Crow, Eagle, Bat
    Answer: Bat (It is a mammal, not a bird)
  14. SSC CGL 2015: Yamuna, Ganga, Krishna, Himalaya
    Answer: Himalaya (It is a mountain, others are rivers)
  15. SSC JE 2021: 2, 4, 6, 9
    Answer: 9 (Odd number, others are even)
  16. SSC CGL 2022: Book, Pen, Pencil, Scale
    Answer: Book (Used for reading, others for writing/drawing)
  17. SSC CHSL 2015: Liver, Kidney, Heart, Bone
    Answer: Bone (Others are internal organs)
  18. SSC GD 2022: Earth, Mars, Venus, Sun
    Answer: Sun (It is a star, others are planets)
  19. RRB NTPC 2020: 36, 49, 64, 99
    Answer: 99 (Not a perfect square)
  20. SSC CGL 2023: Apple, Banana, Grapes, Potato
    Answer: Potato (It is a vegetable)
  21. SSC CHSL 2014: Gold, Silver, Copper, Plastic
    Answer: Plastic (It is not a metal)
  22. SSC CGL 2017: Cricket, Football, Chess, Hockey
    Answer: Chess (It is not a physical/outdoor sport)
  23. HSSC Group D 2019: Lotus, Lily, Rose, Coconut
    Answer: Coconut (Fruit, others are flowers)

Tips to Solve Classification Questions

  • Look for a common feature or logic that connects the majority of items.
  • Think in terms of category (animal, bird, number type, etc.).
  • If numbers are given, check for mathematical patterns (square, cube, prime).
  • Don’t overthink—often the odd one is logically unrelated, not obscure.
  • Practice makes it easier to spot patterns quickly during exams.
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