Classification (Odd One Out)
🔒 Log in to trackClassification questions list four or five similar items and ask which one does not belong. The hidden rule — a shared category, number property or letter structure — must hold for every option except one. CGL asks 2-4 per shift, drawn from number properties, letter clusters, word categories and pairs.
One page per subtopic: detailed notes, every question type, formulas, tricks and practice sets.
Every formula on one printable page, grouped by subtopic.
4 exam-level questions worked step by step.
89 questions — untimed practice or a timed test with analysis.
Track record in the exam
Questions per shift in recent SSC CGL papers.
Test difficulty mix (89 questions)
Question patterns exams keep repeating
Taken from previous-year papers. If a pattern is marked "very common", expect to see it in your exam.
Find the odd one out
very commonFour numbers, letters or words where three share a feature.
Look for a simple feature of three items (even/odd, same type, same pattern).
The item that does not fit is the answer.
2, 4, 6, 9
2, 4 and 6 are even numbers
9 is an odd number
Answer: 9
Odd one out with a second check
commonThe first rule you find fits all four numbers, so you must look deeper.
If the first rule fits all four, check the next property.
Keep checking until one item is different.
121, 169, 225, 289
All are perfect squares: 11², 13², 15², 17²
Look deeper: 11, 13 and 17 are prime numbers
15 is not prime
Answer: 225
Animals and plants
very commonFour words from nearby groups, like animals, birds, fruits or vegetables.
Name the group that three words belong to.
The word from a different group is the answer.
Snake, Lizard, Crocodile, Whale
Snake, Lizard and Crocodile are reptiles
A whale is a mammal
Answer: Whale
Same use or job
commonFour objects or devices, and three do the same kind of job.
Ask 'what does it do?', not 'where is it found?'.
The one with a different job is the answer.
Keyboard, Mouse, Scanner, Monitor
Keyboard, Mouse and Scanner send data into the computer (input)
A Monitor shows data (output)
Answer: Monitor
Prime and non-prime numbers
very commonFour numbers of similar size where three are prime (or three are not).
Test each number by 2, 3, 5 and 7.
Spot the one that is different.
17, 19, 23, 27
17, 19 and 23 are prime
27 = 3 × 9, so it is not prime
Answer: 27
Squares and cubes
commonNumbers that all look special, but one is not a square or cube like the others.
Learn squares up to 20² and cubes up to 12³.
Find which number is not the same kind.
64, 125, 216, 100
64 = 4³, 125 = 5³, 216 = 6³ are all cubes
100 = 10² is a square, but not a cube
Answer: 100
Letter groups with a step
commonFour letter groups where three move by the same step.
Find the step between the letters in each group.
The group with a different step is the answer.
BDF, HJL, NPR, PQR
B→D→F: +2, +2. H→J→L: +2, +2. N→P→R: +2, +2
P→Q→R: +1, +1
Answer: PQR
Word pairs with a different link
very commonFour word pairs, and three have the same link.
Say the link of the first pair in one sentence.
Test every pair with the same sentence.
Cow : Calf, Horse : Foal, Dog : Kitten, Sheep : Lamb
Calf, foal and lamb are the young of cow, horse and sheep
A kitten is the young of a cat, not of a dog
Answer: Dog : Kitten
Pairs with one wrong fact
commonFour pairs like country and capital, and one pair is factually wrong.
All four pairs look alike, so check each fact.
The pair with the wrong fact is the answer.
Rome : Italy, Oslo : Norway, Madrid : Portugal, Cairo : Egypt
Rome is the capital of Italy, Oslo of Norway, Cairo of Egypt
Madrid is the capital of Spain, not Portugal
Answer: Madrid : Portugal
Number sets with the same steps
commonSets of three numbers like (2, 4, 8) and (3, 6, 12), and one set breaks the rule.
Find the step inside each set (×2, +5 and so on).
The set with a different step is the answer.
(2, 4, 8), (3, 6, 12), (5, 10, 20), (4, 9, 16)
(2, 4, 8): ×2, ×2. (3, 6, 12): ×2, ×2. (5, 10, 20): ×2, ×2
(4, 9, 16) is 2², 3², 4², not ×2
Answer: (4, 9, 16)