📑 Topics on this page (Jump to Topic):
📌 1. Method to Find the Odd One
- First find the common group of all four (fruits, planets, primes…).
- Then check sub-properties: colour, use, place, type of number, gap between letters.
- The rule that fits exactly three and not one is the correct rule.
📌 2. Common Bases for Word Classification
| Basis | Example (odd) |
|---|---|
| Planet / Satellite | Mars, Venus, Jupiter, Moon |
| Mammal / Other | Whale, Bat, Dog, Shark |
| Type of instrument | Sitar, Veena, Guitar, Tabla (percussion) |
| Unit | Metre, Inch, Foot, Litre |
| Capital / Country | Paris, Tokyo, Delhi, Brazil |
| Root / stem vegetable | Carrot, Radish, Beetroot, Potato (stem) |
⚠️ Exam Traps:
- Potato is a modified stem (tuber), not a root; tomato is botanically a fruit.
- Bat is a mammal, not a bird; whale is a mammal, not a fish.
📌 3. Number Classification
- Prime / composite, even / odd, perfect square / cube.
- Equal digit sum (e.g. 34, 52, 61 → 7).
- Divisibility by a number (e.g. multiples of 7).
- Number pairs: (3, 10), (4, 17), (5, 26) → n² + 1.
💡 Memory Tip: Memorise primes up to 50: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47. 51 (=3×17), 57 (=3×19), 91 (=7×13) are not prime.
📌 4. Letter-Cluster Classification
- Equal gaps between letters (ACE, GIK: +2 +2).
- Presence/position of vowels (A, E, I, O, U).
- Opposite pairs: AZ, BY, CX (sum 27).
⚠️ Exam Traps:
- An option may have two different gaps (+2, +3) — check the whole cluster, not only the first gap.
📌 5. Practice MCQs
📝 Practice MCQs (prepared by SF Prep — not PYQs)
Q1. Find the odd one out: Practice
Correct answer: (B)
Mars, Venus and Jupiter are planets; the Moon is a satellite.
Mars, Venus and Jupiter are planets; the Moon is a satellite.
Q2. Find the odd one out: Practice
Correct answer: (C)
Whale, bat and dog are mammals; the shark is a fish.
Whale, bat and dog are mammals; the shark is a fish.
Q3. Find the odd one out: Practice
Correct answer: (D)
Metre, inch and foot measure length; litre measures volume.
Metre, inch and foot measure length; litre measures volume.
Q4. Find the odd one out: Practice
Correct answer: (A)
Carrot, radish and beetroot are roots; potato is a modified stem.
Carrot, radish and beetroot are roots; potato is a modified stem.
Q5. Find the odd one out: Practice
Correct answer: (B)
Sitar, veena and guitar are string instruments; tabla is a percussion instrument.
Sitar, veena and guitar are string instruments; tabla is a percussion instrument.
Q6. Find the odd one out: Practice
Correct answer: (C)
Paris, Tokyo and Cairo are capitals; Brazil is a country.
Paris, Tokyo and Cairo are capitals; Brazil is a country.
Q7. Find the odd number: Practice
Correct answer: (D)
37, 41 and 43 are prime; 51 = 3 × 17.
37, 41 and 43 are prime; 51 = 3 × 17.
Q8. Find the odd number: Practice
Correct answer: (A)
36, 64 and 81 are perfect squares; 50 is not.
36, 64 and 81 are perfect squares; 50 is not.
Q9. Find the odd number: Practice
Correct answer: (B)
Digit sums of 34, 52, 61 are 7; that of 45 is 9.
Digit sums of 34, 52, 61 are 7; that of 45 is 9.
Q10. Find the odd number: Practice
Correct answer: (C)
49, 63 and 84 are multiples of 7; 72 is not.
49, 63 and 84 are multiples of 7; 72 is not.
Q11. Find the odd pair: Practice
Correct answer: (D)
Rule n² + 1: 3→10, 4→17, 5→26; for 6 it should be 37, not 35.
Rule n² + 1: 3→10, 4→17, 5→26; for 6 it should be 37, not 35.
Q12. Find the odd pair: Practice
Correct answer: (A)
In (2, 8), (3, 27), (4, 64) the second is the cube of the first; 5³ = 125, not 120.
In (2, 8), (3, 27), (4, 64) the second is the cube of the first; 5³ = 125, not 120.
Q13. Find the odd letter-cluster: Practice
Correct answer: (B)
ACE, GIK, PRT have gaps +2, +2; MOR has +2, +3.
ACE, GIK, PRT have gaps +2, +2; MOR has +2, +3.
Q14. Find the odd letter-pair: Practice
Correct answer: (C)
AZ, BY, CX are opposite letters (positions sum to 27); the opposite of D(4) is W(23), not V.
AZ, BY, CX are opposite letters (positions sum to 27); the opposite of D(4) is W(23), not V.
Q15. Find the odd one out: Practice
Correct answer: (D)
AEI, OUA and EIO contain only vowels; BCD has only consonants.
AEI, OUA and EIO contain only vowels; BCD has only consonants.
Q16. Find the odd one out: Practice
Correct answer: (A)
Parrot, pigeon and sparrow can fly; the penguin cannot.
Parrot, pigeon and sparrow can fly; the penguin cannot.
Q17. Find the odd one out: Practice
Correct answer: (B)
Spinach, fenugreek and bathua are leafy vegetables; tomato is a fruit.
Spinach, fenugreek and bathua are leafy vegetables; tomato is a fruit.
Q18. Find the odd one out: Practice
Correct answer: (C)
The other three measure length; kilogram measures mass.
The other three measure length; kilogram measures mass.
Q19. Find the odd number: Practice
Correct answer: (D)
29, 31 and 47 are prime; 91 = 7 × 13.
29, 31 and 47 are prime; 91 = 7 × 13.
Q20. Find the odd one out: Practice
Correct answer: (A)
Cube, cylinder and sphere are 3-D solids; a triangle is 2-D.
Cube, cylinder and sphere are 3-D solids; a triangle is 2-D.