SOF IMO · Bite-size lessons

Analogy and Classification

About 6 min · Logical Reasoning · English

Time worked out from the lesson's 344 words at 150 words a minute, plus a minute for each question.

Analogy and Classification form a critical pillar of the Logical Reasoning section in SOF IMO. These questions test your ability to recognize patterns, relationships and underlying logic among words, numbers and geometric figures.

Key ideas

• Analogy means similarity or correspondence between two pairs. If A relates to B in a certain way, then C relates to D in the same way. Format: A : B :: C : ?
• Classification means grouping items by a common property, then identifying the element that doesn't belong. Three items share a trait; one does not.
• Number-based patterns include arithmetic operations (sum, difference, product), divisibility rules, squares/cubes, prime/composite classification and place-value manipulation (reverse, digit sum).
• Alphabet-based patterns rely on letter positions (A=1, B=2...Z=26), vowel/consonant classification, alphabetical order and letter shifts (next letter, skip patterns).
• Word-based classification uses semantic categories (fruits, animals, metals), part-of-speech grouping (noun, verb) or functional relationships (tool-action, animal-habitat).

Watch out for

• Surface-level matching: Assuming the first obvious pattern without verifying all options. Fix: Test your rule on every choice; confirm it fits the given pair exactly.
• Ignoring alternate relationships: A number pair might relate by sum, product or digit sum. If one doesn't work, try another. Fix: List possible operations (add, subtract, multiply, square) and test each.
• Mixing up vowels and consonants: Counting Y as a vowel (it's context-dependent but generally a consonant in classification). Fix: Stick to A, E, I, O, U as vowels for IMO problems.

Quick reference

• Analogy format: A : B :: C : D means "A relates to B as C relates to D."
• Classification: Three items share a property; one does not—find the mismatch.
• Number relationships: Check operations (×, +, square), divisibility, prime/composite and digit sums.
• Alphabet relationships: Position values (A=1…Z=26), shifts (+n letters), vowel/consonant groups.
• Word relationships: Synonyms, antonyms, categories (tools, animals, food) and functional pairs (doctor:hospital).

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

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