Classification (Odd One Out)
🔒 Log in to trackPair odd one out
🔒 Log in to trackEach option is a pair, like Cow : Calf or 12 : 144. Three pairs share the same relation and one does not. This is an analogy question in reverse: name the relation the majority shares, then spot the pair that breaks it. The trap is a pair from the same topic with a different relation. Doctor : Hospital sits beside tool pairs, but it is a workplace, not a tool.
What pair classification asks
Each option is a pair: two words, two letters, or a letter and a number. Three pairs share one relationship. One pair is linked differently. You find that pair.
Take Cow : Calf, Dog : Puppy, Cat : Kitten, Horse : Stable. The first three are animal : young one. Horse : Stable is animal : home. So Horse : Stable is odd.
Rule: Make one sentence from a pair, then test all four pairs with the same sentence. Keep the direction of the words.
One sentence, four tests
- 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 stable is the young one of a horse" is false.
- If the sentence fits three pairs, the fourth is the answer.
- If it fits only two pairs, the sentence is wrong. Build a new one from a different pair.
- Keep the direction. "Worker : tool" is not the same as "tool : worker".
Watch: Matching the topic is not enough. All four pairs can be about doctors or animals. Only the relation decides.
Word-pair relation bank
| Relation | Example pairs |
|---|---|
| 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 |
| Opposite meaning | Hot : Cold, Rich : Poor |
| Same meaning | Big : Large, Quick : Fast |
GK pairs: find the wrong fact
Here every pair has the same shape, but one pair states a wrong fact. Kerala : Kochi is wrong, because the capital of Kerala is Thiruvananthapuram.
The wrong pair usually uses a famous city that is not the capital, or the currency of a different country. Use only well-known facts.
Example: Japan : Yen, India : Rupee, Bangladesh : Taka, China : Dollar. China's currency is the yuan, so China : Dollar is odd.
Letter pairs and letter-number pairs
Turn letters into positions (EJOTY: E 5, J 10, O 15, T 20, Y 25).
- Gap check: CF, HK and MP all have a gap of +3. RV has a gap of +4, so RV is odd.
- Opposite check: BY, EV and HS add to 27. KO adds to 26, so KO is odd.
- Letter-number pairs: the number comes from the position. C : 9, E : 25 and G : 49 are squares of positions (3², 5², 7²). H : 60 breaks the rule, because 8² = 64.
Worked example
Odd pair: Carpenter : Saw, Tailor : Needle, Farmer : Plough, Doctor : Hospital.
- Sentence: "the second is the tool the first works with".
- Saw, needle and plough are tools. A hospital is a place, not a tool.
Answer: Doctor : Hospital.
Tip: Every worker has a tool, a place and a product. The setter puts the other two in the options as traps.
Question types you will see
Each type: how to recognise it, the method step by step, and one question to try.
Word pairs: relation break
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.
The setter keeps the topic the same but changes the relation in one pair.
Find the odd pair: Cow : Calf, Dog : Puppy, Cat : Kitten, Horse : Stable.
Show solutionHide solution
Calf, puppy and kitten are young ones of cow, dog and cat.
A stable is the horse's home, not its young one.
Rule: three pairs are animal : young one; one is animal : home.
Horse : Stable
GK pairs: one factually wrong pair
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.
The wrong pair usually uses a famous city that is not the capital, or another country's currency.
Find the odd pair: Japan : Yen, India : Rupee, Bangladesh : Taka, China : Dollar.
Show solutionHide solution
Yen, rupee and taka are the correct currencies of Japan, India and Bangladesh.
China's currency is the yuan, not the dollar.
Rule: three correct currency pairs, one wrong fact.
China : Dollar
Letter pairs (gap or opposite letters)
Options are two-letter pairs such as CF, HK, MP or BY, EV, HS.
Write the 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.
The setter uses one gap, or the 27-sum, for three pairs and changes it slightly for the fourth.
Find the odd pair: CF, HK, MP, RV.
Show solutionHide solution
C→F is +3, H→K is +3, M→P is +3.
R→V is +4.
Rule: three gaps of +3, one gap of +4.
RV
Letter : number pairs
Each option looks 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.
The number is always a simple function of the letter's position, so each formula takes seconds to test.
Find the odd pair: C : 9, E : 25, G : 49, H : 60.
Show solutionHide solution
C is 3rd and 9 = 3². E is 5th and 25 = 5². G is 7th and 49 = 7².
H is 8th, and 8² = 64, not 60.
Rule: three numbers are position², one is not.
H : 60
Synonym vs antonym pairs
Four pairs of ordinary words; three pairs are opposites (or three are same-meaning), and 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.
A synonym pair planted among antonym pairs (or the reverse) breaks the shared kind.
Find the odd pair: Hot : Cold, Up : Down, Rich : Poor, Big : Large.
Show solutionHide solution
Hot-Cold, Up-Down and Rich-Poor are opposites.
Big and Large mean the same thing.
Rule: three opposite pairs, one same-meaning pair.
Big : Large
Shortcuts that save time
Form the relation sentence from the three pairs that clearly agree, then tick or cross all four options. In number pairs, compute the rule for each pair; three will match.
Find the odd pair: 3 : 9, 7 : 49, 9 : 81, 11 : 132.
Show solutionHide solution
3 : 9, 7 : 49 and 9 : 81 follow n : n².
11² = 121, but the pair says 132.
Rule: three pairs are squares, one is not.
11 : 132
Mistakes to avoid
Where most students lose marks on this subtopic.
Matching topics instead of relations (all pairs about doctors, only three tool : user).
Say the relation as a sentence. The topic is a decoy.
Testing the relation only on the pair that looks odd.
Test the sentence on all four pairs, in the same direction.
Ignoring the order of the words (tool : worker taken as worker : tool).
Keep the direction of the model sentence in every pair.
Missing a wrong GK fact because the shape of the pair looks right.
In GK pairs, check each fact itself, not the shape.
In letter-number pairs, stopping at the first formula that fits one pair.
Try position, 2 × position, position² and 27 − position, then confirm on a second pair.
Quick revision
Read this the night before the exam.
One relation sentence, tested on all four pairs in the same direction.
Same topic does not mean same relation.
GK pairs: find the factually wrong pair (Kochi is not Kerala's capital).
Letter pairs: check the gap, then the 27-sum.
Letter-number pairs: position, 2 × position, position², 27 − position.
Number pairs: compute the rule for each pair; three match, one breaks.
Practice: 13 questions
Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.
Topic test · 13 questions
Suggested time 7 min · wrong answers go to your mistake notebook automatically.