Odd One Out Classification Questions for SSC CGL: The Short Answer
Classification (also called odd one out) questions give four or five words, numbers, letter groups or pairs, and all except one share a common property. You must pick the one that does not belong. The method is: find the property shared by at least three items first, then check that exactly one item breaks it. For numbers, test prime, square, cube, divisibility and digit patterns; for letters, write the alphabet positions; for words, ask "what kind of thing is each?"
Key takeaway for SSC: SSC CGL and CHSL Tier 1 usually ask 2 to 4 classification questions (word, number, letter and pair types), and SSC MTS, GD and RRB NTPC ask several more. They are among the fastest marks in reasoning when you know the common properties listed below. Every number and letter example here was checked in Python.
Classification uses the same logic as analogy, so read our analogy questions for SSC CGL and coding decoding tricks for SSC CGL with this note.
Types of Classification Questions in Reasoning
| Type | What you compare | Example (odd one in bold) |
|---|---|---|
| Word classification | Category, use, habitat, gender, place | Rose, Lily, Lotus, Mango |
| Number classification | Prime, square, cube, divisibility, digits | 17, 23, 29, 35, 41 |
| Letter-group classification | Positions, gaps, opposite letters, vowels | ACE, BDF, GIK, MNO |
| Number-pair classification | Same rule inside each pair | 3 : 10, 4 : 17, 5 : 26, 6 : 35 |
| Word-pair classification | Same relationship inside each pair | Doctor : Hospital, Teacher : School, Pen : Ink, Judge : Court |
| Figure classification | Shapes, rotation, number of lines | (non-verbal; check sides, shading, arrows) |
How to Solve Odd One Out Questions (4-Step Method)
- Look for the obvious category (all fruits, all metals, all capitals).
- If nothing is obvious, list a property for each item (number of letters, vowel count, positions, prime or not).
- Find the property that three or four items share; the item without it is the answer.
- Check for a second pattern. If two different items could be odd for two different reasons, choose the more specific, exam-standard property (for example, "not a prime" over "has an even digit").
Word Classification Questions (Common Categories)
| Category | Group | Odd one example |
|---|---|---|
| Flowers vs fruit | Rose, Lily, Lotus, Mango | Mango (fruit) |
| Metals vs non-metal | Iron, Copper, Zinc, Sulphur | Sulphur (non-metal) |
| Planets vs star | Mars, Venus, Jupiter, Sun | Sun (a star) |
| Instruments that measure | Thermometer, Barometer, Ammeter, Microscope | Microscope (magnifies, does not measure) |
| Herbivores vs carnivore | Cow, Goat, Deer, Tiger | Tiger |
| Mammals vs fish | Whale, Dolphin, Bat, Shark | Shark (a fish; the others are mammals) |
| Capital cities | Mumbai, Chennai, Kolkata, Pune | Pune (not a state capital) |
| Sense organs | Eye, Ear, Nose, Heart | Heart |
| Musical instruments: string | Sitar, Veena, Sarod, Tabla | Tabla (percussion) |
Example 1: Choose the odd one: Whale, Dolphin, Bat, Shark.
Whale, dolphin and bat are mammals; a shark is a fish. Answer: Shark.
Example 2: Choose the odd one: Thermometer, Barometer, Ammeter, Microscope.
The first three measure something (temperature, pressure, current). A microscope magnifies. Answer: Microscope.
Number Classification Tricks (Prime, Square, Cube)
| Property to test | Example set | Odd one |
|---|---|---|
| Prime numbers | 17, 23, 29, 35, 41 | 35 (= 5 × 7) |
| Perfect squares | 16, 25, 36, 48, 64 | 48 |
| Perfect cubes | 8, 27, 64, 100, 125 | 100 |
| Multiples of 6 | 12, 18, 24, 32, 36 | 32 |
| Multiples of 7 | 42, 63, 84, 95, 112 | 95 |
| Prime vs composite | 2, 3, 5, 9, 11 | 9 |
Example 3: Choose the odd number: 17, 23, 29, 35, 41.
All except 35 are prime; 35 = 5 × 7. Answer: 35.
Example 4: Choose the odd number: 8, 27, 64, 100, 125.
8 = 2³, 27 = 3³, 64 = 4³, 125 = 5³; 100 is not a cube. Answer: 100.
Trick: 64 is both a square and a cube, so check every option against both properties before answering.
Letter Group Classification (Alphabet Position Trick)
Write each letter's position (A = 1 … Z = 26) or use EJOTY (E 5, J 10, O 15, T 20, Y 25).
Example 5: Choose the odd group: ACE, BDF, GIK, MNO.
ACE (1, 3, 5), BDF (2, 4, 6), GIK (7, 9, 11) skip one letter each time. MNO (13, 14, 15) has consecutive letters. Answer: MNO.
Example 6: Choose the odd group: BY, CX, DW, EU.
BY (2 + 25), CX (3 + 24), DW (4 + 23) are opposite-letter pairs adding to 27. EU = 5 + 21 = 26. Answer: EU.
| Letter pattern | How to test |
|---|---|
| Same gap (+2, +3) | Differences between positions |
| Opposite pairs | Positions add up to 27 |
| Vowel position | Count or position of vowels |
| Reverse order | Check if one group runs backwards |
| Mirror pairs (AZ, BY) | Sum = 27 |
Number Pair and Word Pair Classification
Example 7: Choose the odd pair: 3 : 10, 4 : 17, 5 : 26, 6 : 35.
Rule n : n² + 1 gives 3 : 10, 4 : 17, 5 : 26 and 6 : 37. The pair 6 : 35 is 6² − 1. Answer: 6 : 35.
Example 8: Choose the odd pair: Doctor : Hospital, Teacher : School, Pen : Ink, Judge : Court.
Three pairs are person : workplace. Pen : Ink is object : what it uses. Answer: Pen : Ink.
Figure Classification Basics (Non-Verbal Odd One Out)
In figure classification, four or five figures are shown and one differs. Check these features in order, one at a time:
| Feature | What to check |
|---|---|
| Number of sides or lines | Triangle (3), square (4), pentagon (5): is one figure's count different? |
| Rotation | Three figures may be rotations of one shape, while the odd one is a mirror image |
| Shading | Count shaded parts or check which part is shaded |
| Position of a small element | Dot or arrow inside vs outside, or clockwise vs anticlockwise position |
| Open vs closed figures | One figure may have a gap the others do not |
Tip: if three figures are the same shape turned by 90°, the odd one is usually the flipped (mirror) version, which cannot be produced by rotation alone.
Classification When Meaning Is the Same (Letter-Count Trick)
Sometimes all words belong to one category, so the odd one depends on spelling. Check the number of letters, vowels, or whether the word starts and ends with a vowel.
Example 9: Choose the odd word: TABLE, CHAIR, SOFA, BENCH.
All are furniture, so meaning does not decide it. TABLE, CHAIR and BENCH have 5 letters; SOFA has 4. Answer: SOFA.
Odd One Out Tricks: Common Traps
- Two possible answers. Prefer the clearer, exam-standard property (prime, square, category).
- Squares that are also cubes (64, 729) and 1 (square and cube of itself).
- Bats and whales are mammals, not birds or fish.
- Tomato is botanically a fruit, but exam word groups usually treat it as a vegetable; read the other options to see which sense is used.
- Count letters carefully in letter-count questions (for example, "Banana" has 6 letters, 3 vowels).
Odd One Out Classification Questions (Practice Set with Answers)
- Choose the odd one: Iron, Copper, Zinc, Sulphur. Answer: Sulphur. It is a non-metal.
- Choose the odd one: Mars, Venus, Jupiter, Sun. Answer: Sun. It is a star.
- Choose the odd number: 16, 25, 36, 48, 64. Answer: 48. Not a perfect square.
- Choose the odd number: 12, 18, 24, 32, 36. Answer: 32. Not a multiple of 6.
- Choose the odd number: 42, 63, 84, 95, 112. Answer: 95. Not a multiple of 7.
- Choose the odd one: Cow, Goat, Deer, Tiger. Answer: Tiger. Carnivore; the rest are herbivores.
- Choose the odd one: Sitar, Veena, Sarod, Tabla. Answer: Tabla. Percussion; the rest are string instruments.
- Choose the odd number: 2, 3, 5, 9, 11. Answer: 9. Not prime.
- Choose the odd group: AZ, BY, CX, DV. Answer: DV. AZ, BY and CX add to 27 (opposite letters); D (4) + V (22) = 26.
- Choose the odd one: Eye, Ear, Nose, Heart. Answer: Heart. Not a sense organ.
For timed practice, take the SSC CGL Reasoning Mini Mock Test 05 and the SSC CGL Analogy Mock Test 01.
Odd One Out Classification FAQs
What is classification in reasoning?
It is a question type where all items except one share a common property. You identify that property and choose the item that does not have it, which is why it is also called odd one out.
How do you solve odd one out questions quickly?
Look for a common category first. If none is obvious, write a property next to each item (prime, square, letter positions, category) and pick the item that breaks the property shared by the rest.
How do you solve number classification questions?
Test the most common number properties in order: prime, perfect square, perfect cube, divisibility by a common number, and digit sum or digit product.
What is the difference between analogy and classification?
Analogy completes a pair with the same relationship (A : B :: C : ?). Classification finds the one item that does not share the group's common property.
How many classification questions come in SSC CGL?
Usually 2 to 4 in SSC CGL Tier 1 reasoning across word, number, letter and figure types. SSC CHSL, MTS and GD ask a similar number.
What if two options seem odd?
Look for the property that fits exactly three (or four) items and is the most specific. Exams are set so that only one standard property gives a unique answer.
Practice Next
- Mock tests: SSC CGL Reasoning Mini Mock Test 05, SSC CGL Analogy Mock Test 01, SSC CHSL Reasoning Mini Mock Test 03 and SSC CGL Reasoning Mini Mock Test 02, plus SSC CHSL Classification Mock Test 01.
- Related notes: analogy questions for SSC CGL, coding decoding tricks for SSC CGL, Venn diagram questions for SSC CGL and number system for SSC CGL.
- Exam details: SSC CGL 2026 and SSC CHSL 2026.
- Browse all study notes.