Example 1
Find the odd one out: 17, 37, 23, 87
Answer: D) 87
All others are prime numbers; 87 is composite.
Classification (Odd One Out) reasoning questions for competitive exams: rules, worked examples and practice
Classification (odd one out) questions show items that share a property, except one. Find the property, then the item that breaks it.
Key rules and formulas
- Number checks: prime or composite, odd or even, squares, cubes, multiples, digit sums.
- Word checks: category, meaning, letter pattern.
- Letter-group checks: gaps between letters, vowels, reverse order.
- If two properties fit, choose the one that leaves exactly one item out.
Common traps
- Stopping at the first property that fits only some items.
- Missing that 1 is neither prime nor composite.
Where Classification (Odd One Out) is asked
- RRB Group D (General Intelligence & Reasoning)
- RRB NTPC CBT 1 (General Intelligence & Reasoning)
- SSC CGL Tier 1 (General Intelligence & Reasoning)
- SSC CGL Tier 2 (General Intelligence, Reasoning & General Intelligence)
- SSC CHSL Tier 1 (General Intelligence)
Worked examples
Example 2
Find the odd one out: 77, 17, 37, 61
Answer: D) 77
All others are prime numbers; 77 is composite.
Example 3
Find the odd one out: 37, 87, 29, 59
Answer: A) 87
All others are prime numbers; 87 is composite.
Frequently asked questions
What is Classification (Odd One Out) in competitive exams?
Classification (odd one out) questions show items that share a property, except one. Find the property, then the item that breaks it.
Which exams ask Classification (Odd One Out) questions?
On MockBazaar, Classification (Odd One Out) questions appear in RRB Group D, RRB NTPC CBT 1, SSC CGL Tier 1, SSC CGL Tier 2, SSC CHSL Tier 1.
What is the most common mistake in Classification (Odd One Out)?
Stopping at the first property that fits only some items.