Classification
Classification (Odd One Out)
SSC and RRB papers carry 4-6 classification questions per paper, making this one of the highest-frequency reasoning topics. Each question presents four or five items where one breaks the grouping rule shared by the rest. You will encounter semantic, number, letter-pattern, and code-based subtypes across SSC CGL, SSC CHSL, and IBPS Clerk. Mastering all four subtypes ensures you do not lose easy marks.
Key Idea
Find the property shared by the majority — not just any two items — and the one item that breaks that property is the odd one out.
Core Rules
Semantic Group Rule
List what each word represents; find the category shared by all but one (e.g., planets, metals, rivers); the item outside that category is odd
Start with this rule when all items are common nouns and you can identify a clear superordinate category.
Number Property Rule
Check prime, composite, perfect square, cube, odd, even, multiple, or digit-sum properties; the number that breaks the shared property is odd
Apply this when the items are numbers and no semantic category exists — test mathematical properties one by one.
Letter Pattern Rule
Check position of letters (A=1…Z=26), gap between letters, vowel/consonant count, or alphabetical order; one group violates the pattern
When items are letter-groups like BDF, CFI, EGJ, and you need the deviation.
Code Pattern Rule
Decode each item using the coding logic; the item whose decoded value does not match the others' rule is the odd one
When items are symbol or digit codes and a hidden substitution cipher is present.
Multiple Groupings Trap
When two plausible groupings exist, pick the one that unites the largest number (3 or 4 out of 5) — exam questions always have exactly one valid majority grouping
When you can justify more than one item as odd; choose the answer that leaves the tightest group.
Relevant Exams
Classification is among the highest-frequency topics in SSC and RRB papers — typically 4–6 questions per paper spanning semantic, number, and letter subtypes. Mastery of all four subtypes is essential.