Classification • Odd one out (words, numbers, figures)
1. Introduction to Classification
Classification is a process of grouping items based on common properties or characteristics. The aim is to identify the element that does not belong to the group due to differing characteristics—thus termed as the Odd One Out.
2. Types of Classification Questions
a) Word-Based Classification
These questions are based on meaning, function, nature, or category of words.
Examples:
Rose, Lily, Lotus, Mango
Mango is the odd one as all others are flowers, while Mango is a fruit.
Teacher, Lawyer, Engineer, Hospital
Hospital is the odd one out because it is a place, while others are professions.
b) Number-Based Classification
These rely on mathematical or numerical logic such as prime numbers, even/odd, perfect squares, etc.
Examples:
3, 7, 11, 15
15 is the odd one; others are prime numbers.
64, 125, 343, 729, 500
500 is the odd one; others are perfect cubes (4^3 = 64, 5^3 = 125, etc.)
c) Letter-Based Classification
Here, groups of letters are given and classification is based on the position of letters in the alphabet.
Examples:
AB, CD, EF, FG
FG is the odd one; the rest have one-letter gaps (A-C, C-E, E-G), but F-G are consecutive.
d) Figure-Based Classification
These include visual patterns or shapes. You need to identify the one that is structurally or logically different.
Examples:
Four figures might be shown with similar geometric shapes and one with a rotation or missing component.
Three figures may be symmetrical, and one asymmetrical.
e) Miscellaneous Classification
Sometimes based on general knowledge, such as currency, capitals, elements, units of measurement.
Example:
Yen, Dollar, Euro, Asia
Asia is the odd one; others are currencies.
3. Key Concepts and Tips
Understand categories clearly: professions, animals, vehicles, etc.
Check for hidden patterns: alphabetical order, arithmetic progression.
Be wary of visual similarities in figure-based questions.
Look for exceptions logically, not just visually.
Always double-check the commonality before deciding the odd one.
4. Detailed Examples with Explanations
Word-Based: Q: Apple, Banana, Carrot, Mango
Carrot is a vegetable, rest are fruits. So, Carrot is the odd one.
Number-Based: Q: 11, 13, 17, 20
All except 20 are prime numbers. So, 20 is the odd one.
Figure-Based:
Suppose three figures are triangles rotated at different angles and one is a square.
The square is structurally different. Hence, the odd one.
Dog, Cat, Cow, Car
❌ Car – Others are animals.-
Table, Chair, Sofa, Shirt
❌ Shirt – Others are furniture. -
Rose, Lotus, Lily, Apple
❌ Apple – Others are flowers. -
Iron, Copper, Plastic, Gold
❌ Plastic – Others are metals. -
Pen, Pencil, Paper, Apple
❌ Apple – Others are stationery. -
Physics, Chemistry, Biology, History
❌ History – Others are science subjects. -
Asia, Africa, London, Europe
❌ London – Others are continents. -
Monday, Friday, Sunday, April
❌ April – Others are days. -
Eagle, Parrot, Sparrow, Bat
❌ Bat – Others are birds; bat is a mammal. -
Red, Green, Square, Blue
❌ Square – Others are colors. -
Teacher, Lawyer, Doctor, Office
❌ Office – Others are professions. -
Gold, Silver, Mercury, Diamond
❌ Diamond – Others are metals. -
Bread, Rice, Noodles, Milk
❌ Milk – Others are solid staple foods. -
Pen, Ink, Eraser, Calculator
❌ Calculator – Others are manual writing tools. -
Foot, Hand, Elbow, Shoulder
❌ Foot – Others are upper body parts. -
Truck, Car, Train, Road
❌ Road – Others are vehicles. -
Potato, Tomato, Radish, Carrot
❌ Tomato – Others are roots; tomato is a fruit. -
Fire, Smoke, Water, Air
❌ Smoke – Others are elements or states of matter. -
Paper, Wood, Plastic, Pen
❌ Pen – Others are materials. -
Ball, Bat, Stump, Helmet
❌ Helmet – Others are direct playing equipment. -
Knife, Gun, Sword, Armor
❌ Armor – Others are offensive weapons. -
India, China, Japan, Delhi
❌ Delhi – Others are countries. -
Teacher, Student, Headmaster, Book
❌ Book – Others are people involved in school. -
Shampoo, Soap, Toothpaste, Chocolate
❌ Chocolate – Others are toiletries. -
Earth, Mars, Moon, Jupiter
❌ Moon – Others are planets; Moon is a satellite.
🔹 SECTION B: Number-Based Classification (25 Questions)
-
2, 4, 6, 9
❌ 9 – Others are even. -
11, 13, 15, 17
❌ 15 – Others are primes. -
21, 63, 105, 143
❌ 143 – Others are divisible by 7. -
36, 49, 64, 72
❌ 72 – Others are perfect squares. -
5, 15, 25, 40
❌ 40 – Not a multiple of 5. -
27, 64, 125, 248
❌ 248 – Others are cubes. -
1, 4, 9, 12
❌ 12 – Others are perfect squares. -
101, 103, 107, 111
❌ 111 – Not a prime number. -
28, 36, 45, 49
❌ 49 – Only perfect square. -
18, 21, 24, 29
❌ 29 – Only prime. -
14, 28, 56, 108
❌ 108 – Not a multiple of 14. -
32, 64, 96, 121
❌ 121 – Not a multiple of 32 or 16; 121 = 11². -
8, 16, 32, 66
❌ 66 – Not power of 2. -
3, 9, 27, 30
❌ 30 – Not a power of 3. -
81, 121, 144, 169
❌ 121 – All perfect squares, but 121 = 11² (prime square), others are non-prime squares. -
22, 33, 44, 57
❌ 57 – Not divisible by 11. -
13, 17, 23, 35
❌ 35 – Not a prime. -
30, 40, 50, 65
❌ 65 – Not multiple of 10. -
125, 216, 343, 500
❌ 500 – Not a perfect cube. -
7, 14, 21, 31
❌ 31 – Not a multiple of 7. -
19, 29, 39, 49
❌ 49 – Not a prime. -
10, 100, 1000, 1001
❌ 1001 – Not power of 10. -
3, 6, 12, 25
❌ 25 – Not multiple of 3. -
6, 12, 24, 37
❌ 37 – Not multiple of 6. -
64, 128, 256, 400
❌ 400 – Not power of 2.
🔹 SECTION C: Letter/Alphabet-Based Classification (25 Questions)
-
AB, CD, EF, FG
❌ FG – Others have one-letter gap. -
LM, NO, PQ, AB
❌ AB – Others are middle-letter sequences. -
AZ, BY, CX, DW
✅ Pattern – Z to A, Y to B... (No odd one) -
ACE, BDF, EGI, HKJ
❌ HKJ – Doesn't follow same pattern. -
MN, OP, QR, ST
✅ All sequential – No odd one. -
AB, BC, CD, DF
❌ DF – Skips E. -
KL, LM, MN, NP
❌ NP – P is not next to N alphabetically. -
AC, EG, IK, MO
❌ MO – O not consistent with previous skips. -
BF, DJ, HL, NR
✅ All use even skipping pattern – No odd one. -
PQ, RS, TU, VX
❌ VX – Skips W. -
AA, BB, CC, CD
❌ CD – Not two same letters. -
XW, YZ, UV, AB
❌ YZ – All decreasing except YZ. -
EF, GH, IJ, KM
❌ KM – Skips L. -
AZ, BY, CX, DW
✅ No odd one – All mirrored. -
BA, DC, FE, HG
✅ All reversed – No odd one. -
QR, ST, UV, WY
❌ WY – Skip of 1. -
OP, QR, ST, UX
❌ UX – Not consistent sequence. -
LM, NO, PQ, RT
❌ RT – Skips S. -
JK, KL, LM, MQ
❌ MQ – Not sequential. -
AC, BD, CE, DF
❌ DF – Doesn’t match symmetry. -
AB, AD, AH, AK
❌ AK – Skips too many letters. -
XY, YZ, ZA, AB
❌ ZA – Breaks normal sequence. -
FG, GH, HI, IJ
✅ All consistent. -
CD, EF, GH, HJ
❌ HJ – J is inconsistent. -
MN, NP, PR, RT
❌ RT – Not same jump.
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