Classification (Odd One Out)
🔒 Log in to trackPair odd one out
🔒 Log in to trackEach option is a pair (word:word or number:number). Three pairs share the same relation; one does not. The method is exactly the analogy method — name the majority relation, then test each pair against it:
- Word pairs: worker-workplace, creator-creation, animal-home, instrument-quantity.
- Number pairs: b = k·a ± r, reversal (27:72), squares (5:25), multiples.
- Letter pairs: constant shift (AB:DE is +3/+3... test!), opposite letters.
The trap is a pair with the same topic but a different relation — 'Painter : Canvas' sits beside creator-creation pairs but is creator-surface.
Detailed notes
What is pair classification?
Each option is a pair: two words, two letters, or a letter and a number, joined by a colon (Cow : Calf). Three pairs are linked by the same relationship. One pair is linked in a different way. You must find that pair.
This is really an analogy question in reverse. In analogy you copy one relation; here you find the relation three pairs share and spot the pair that breaks it.
Everyday example: Cow : Calf, Dog : Puppy, Cat : Kitten, Horse : Stable. The first three are animal : its young one. Horse : Stable is animal : its home. So Horse : Stable is odd.
Step-by-step method
- Take the first pair and make a short sentence: "A calf is the young one of a cow."
- Put the other pairs into the same sentence: "A puppy is the young one of a dog" ✓, "A stable is the young one of a horse" ✗.
- If the sentence fits three pairs, the fourth is the answer.
- If the sentence fits only two, your sentence is wrong - make a new sentence from the second pair and try again.
- Keep the direction. "Worker : tool" is not the same as "tool : worker".
Word-pair relations you must know
| Relation | Example pair |
|---|---|
| Animal : young one | Goat : Kid, Lion : Cub |
| Animal : home | Horse : Stable, Bee : Hive |
| Worker : tool | Carpenter : Saw, Tailor : Needle |
| Worker : workplace | Doctor : Hospital, Chef : Kitchen |
| Tool : action | Knife : Cut, Broom : Sweep |
| Creator : creation | Author : Book, Sculptor : Statue |
| Instrument : quantity measured | Ammeter : Current, Barometer : Pressure |
| Country : currency | Japan : Yen, Bangladesh : Taka |
| State : capital | Bihar : Patna, Assam : Dispur |
| Word : opposite | Hot : Cold, Rich : Poor |
| Word : same meaning | Big : Large, Quick : Fast |
General-knowledge pairs
Here the relation is simple (state : capital, country : currency) but one pair is factually wrong. Example: Kerala : Kochi - Kochi is a big city, but the capital of Kerala is Thiruvananthapuram. Use only well-known facts; the wrong pair is usually a famous city that is not the capital, or a currency of a different country.
Letter pairs
Turn letters into positions (A = 1 ... Z = 26; EJOTY: E 5, J 10, O 15, T 20, Y 25).
- Constant gap: CF, HK, MP all have gap +3; RV has +4.
- Opposite letters: BY, EV, HS add up to 27; KO adds to 26.
Letter : number pairs
The number is made from the letter's position. C : 9, E : 25, G : 49 use the square of the position (3², 5², 7²). H : 60 breaks it (8² = 64). Other common rules: 2 × position, position + constant, reverse position (27 − position).
Worked example
Odd pair: Carpenter : Saw, Tailor : Needle, Farmer : Plough, Doctor : Hospital.
- Sentence: "A carpenter works with a saw" (worker : tool).
- Tailor works with a needle ✓, farmer works with a plough ✓, doctor works with a hospital ✗ - a hospital is where a doctor works.
- Answer: Doctor : Hospital.
Quick revision
- Make one clear sentence from a pair, then test all four pairs.
- Keep the order of the two words the same as in the sentence.
- Similar topic does not mean same relation (Painter : Canvas is creator : surface, not creator : creation).
- Letter pairs: find the gap or check the 27-sum.
- Letter : number pairs: try position, 2 × position, position², 27 − position.
- GK pairs: find the one factually wrong pair.
Types of questions asked
Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.
Type 1: Word pairs: relation breakvery common3 practice Q
Four word pairs like 'Cow : Calf'. Three share a relation (young one, tool, workplace, creation); one uses a different relation.
- Make a sentence from one pair ('X is the young one of Y').
- Put every pair into the same sentence.
- The pair that does not fit is odd.
Why it works: the setter keeps the topic the same but changes the relation in one pair.
Example: Find the odd pair: Cow : Calf, Dog : Puppy, Cat : Kitten, Horse : Stable.
Three pairs are animal : young one. A stable is the horse's home. Answer: Horse : Stable.
Type 2: GK pairs: one factually wrong paircommon3 practice Q
Pairs of state : capital, country : currency or instrument : quantity. All pairs follow the same relation, but one pair has a wrong fact.
- Check each pair against the fact you know.
- The pair where the fact is wrong is odd.
Why it works: the wrong pair usually uses a famous city (not the capital) or the currency of another country.
Example: Find the odd pair: Japan : Yen, India : Rupee, Bangladesh : Taka, China : Dollar.
Yen, rupee and taka are the correct currencies. China's currency is the yuan (renminbi), not the dollar. Answer: China : Dollar.
Type 3: Letter pairs (gap or opposite letters)common2 practice Q
Options are two-letter pairs such as CF, HK, MP or BY, EV, HS.
- Write positions of both letters.
- Find the gap (second − first) or the sum (27 means opposite letters).
- The pair with a different gap or sum is odd.
Why it works: the setter uses one gap or the 27-sum for three pairs and changes it by one for the fourth.
Example: Find the odd pair: CF, HK, MP, RV.
Gaps: C→F +3, H→K +3, M→P +3, R→V +4. Answer: RV.
Type 4: Letter : number pairscommon2 practice Q
Each option is like 'C : 9' - a letter and a number made from its position.
- Write the position of each letter.
- Try: position, 2 × position, position², position + k, 27 − position.
- The pair whose number does not fit is odd.
Why it works: the number is always a simple function of the letter's position.
Example: Find the odd pair: C : 9, E : 25, G : 49, H : 60.
C = 3 → 9 = 3², E = 5 → 25 = 5², G = 7 → 49 = 7². H = 8 → 8² = 64, not 60. Answer: H : 60.
Type 5: Synonym vs antonym pairsoccasional2 practice Q
Four pairs of ordinary words; three pairs are opposites (or three are same-meaning), one is the other kind.
- Decide for each pair: same meaning or opposite meaning?
- Three will be the same kind.
- The pair of the other kind is odd.
Why it works: a synonym pair is planted among antonym pairs (or the reverse).
Example: Find the odd pair: Hot : Cold, Up : Down, Rich : Poor, Big : Large.
Hot-Cold, Up-Down and Rich-Poor are opposites. Big and Large mean the same. Answer: Big : Large.
Shortcut tricks
⚡ Relation sentence, then four ticks
Form the relation sentence from three pairs that clearly agree, then tick/cross all four options. In number pairs, compute k and r for each pair — three will match.
Example: Q. 3:9, 7:49, 9:81, 11:132
Sol. 3:9, 7:49, 9:81 are n:n². 11² = 121, but the pair says 132 → 11:132.
One relation sentence + four quick ticks settles pair classification.
Where students lose marks
Matching topics instead of relations (all four pairs about artists, only three creator-creation).
In number pairs, testing the relation only on the odd-looking pair and not on the other three.
Missing sign: 12:6 and 18:9 are 'half', while 20:10 fits too — but 14:7 + 'half' means 9:3 does not; direction matters.
Practice sets — 13 questions
Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.
Topic test · 13 questions
Suggested time 7 min · wrong answers go to your mistake notebook automatically.