Odd-One-Out & Classification
17 Class 6 IMO Mathematics Olympiad practice questions on odd-one-out & classification, part of the Patterns & Sequences topic area. Every question below includes the correct answer and a full explanation.
Practice this topic interactively →1. Which is the odd one out?
- A.3
- B.5
- C.7
- D.8
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Answer: D. 8
3, 5, and 7 are all odd numbers; 8 is even.
2. Which is the odd one out?
- A.Apple
- B.Banana
- C.Carrot
- D.Mango
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Answer: C. Carrot
Apple, Banana, and Mango are fruits; a Carrot is a vegetable.
3. Which is the odd one out?
- A.Rose
- B.Lily
- C.Sunflower
- D.Oak
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Answer: D. Oak
Rose, Lily, and Sunflower are flowers; Oak is a tree.
4. Which is the odd one out?
- A.16
- B.25
- C.36
- D.54
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Answer: D. 54
16, 25, and 36 are all perfect squares (4², 5², 6²); 54 is not.
5. Which is the odd one out?
- A.Dog
- B.Cat
- C.Lion
- D.Sparrow
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Answer: D. Sparrow
Dog, Cat, and Lion are mammals; a Sparrow is a bird.
6. Which is the odd one out?
- A.Square
- B.Rectangle
- C.Triangle
- D.Rhombus
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Answer: C. Triangle
Square, Rectangle, and Rhombus all have 4 sides; a Triangle has 3.
7. Which is the odd one out?
- A.4
- B.9
- C.16
- D.20
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Answer: D. 20
4, 9, and 16 are perfect squares; 20 is not.
8. Which is the odd one out?
- A.12
- B.18
- C.24
- D.35
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Answer: D. 35
12, 18, and 24 are multiples of 6; 35 is not.
9. Which is the odd one out?
- A.Cube
- B.Sphere
- C.Cone
- D.Square
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Answer: D. Square
Cube, Sphere, and Cone are 3D solids; a Square is a flat (2D) shape.
10. Which is the odd one out?
- A.2
- B.3
- C.5
- D.9
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Answer: D. 9
2, 3, and 5 are prime numbers; 9 = 3×3 is not.
11. Which is the odd one out?
- A.January
- B.March
- C.April
- D.July
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Answer: C. April
January, March, and July have 31 days; April has only 30.
12. Which is the odd one out?
- A.10
- B.15
- C.20
- D.23
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Answer: D. 23
10, 15, and 20 are multiples of 5; 23 is not.
13. Which is the odd one out?
- A.Triangle
- B.Pentagon
- C.Hexagon
- D.Circle
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Answer: D. Circle
Triangle, Pentagon, and Hexagon are polygons with straight sides; a Circle has none.
14. Which is the odd one out?
- A.Metre
- B.Litre
- C.Kilometre
- D.Centimetre
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Answer: B. Litre
Metre, Kilometre, and Centimetre all measure length; a Litre measures volume.
15. Which is the odd one out?
- A.Whale
- B.Dolphin
- C.Shark
- D.Bat
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Answer: C. Shark
Whale, Dolphin, and Bat are mammals; a Shark is a fish.
16. Which is the odd one out?
- A.8
- B.27
- C.64
- D.90
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Answer: D. 90
8, 27, and 64 are perfect cubes (2³, 3³, 4³); 90 is not.
17. Which is the odd one out: 8, 27, 64, 100, 125?
- A.64
- B.27
- C.8
- D.100
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Answer: D. 100
8, 27, 64, and 125 are perfect cubes (2³, 3³, 4³, 5³); 100 is not.