Start practising

Topic / 60 questions

Classification (Odd One Out) MCQs

Classification (Odd One Out) MCQs are multiple-choice questions that give four numbers, letter groups or words, three of which share a property, and ask you to find the one that does not belong. Every question on MCQs360 shows its correct answer instantly, so you can confirm the shared property and learn the patterns examiners use.

Advertisement
Advertisement
Advertisement

About Classification (Odd One Out) MCQs

Number questions rely on properties such as perfect squares and cubes, primes, multiples of a number, digit sums and even or odd values. Letter group questions use fixed gaps between letters, such as each letter being five places after the one before, so one group breaks the pattern. Others use positions in the reverse alphabet or letters placed in alphabetical order. Converting each letter to its number is the fastest way to see which group does not fit.

Word questions group items by category: body organs, units of mass and volume, plane and solid shapes, fish and mammals, and similar sets. Some answers depend on a single detail, such as a dolphin being a mammal among fish. Classification questions appear in MDCAT, NTS, ISSB intelligence tests and SSC and bank exams, and they reward general knowledge as well as pattern skills.

Key facts to remember

  • A prime number has exactly two factors, 1 and itself; 1 is not a prime number.
  • 121, 144, 484, 529, 576, 625 and 841 are perfect squares (11², 12², 22², 23², 24², 25² and 29²).
  • A dolphin is a mammal, not a fish, which makes it a frequent odd-one-out answer.
  • The kilogram, gram and tonne measure mass, while the litre measures volume.
  • A cylinder is a three-dimensional solid, while a square, triangle and pentagon are two-dimensional shapes.

Exams that include Classification (Odd One Out) MCQs

Pakistan

  • MDCAT
  • NTS
  • GAT
  • ISSB
  • Army, Navy and PAF initial tests
  • PPSC
  • FPSC

India

  • SSC CGL
  • SSC CHSL
  • IBPS PO
  • IBPS Clerk
  • SBI PO
  • SBI Clerk
  • RRB NTPC
  • CAT

Bangladesh

  • BCS
  • Bangladesh Bank recruitment tests

How to prepare for Classification (Odd One Out) MCQs

  1. For numbers, test the common properties in order: squares, cubes, primes, divisibility and digit sums.
  2. For letter groups, convert letters to alphabet positions and compare the gaps in each group.
  3. For words, name the category of three items in one word, then check which item does not fit.
  4. If two options seem odd, look for a more precise property that only three options share.

Frequently asked questions

How do I find the odd number out?

Check whether three numbers are squares, cubes or primes, whether they are multiples of the same number, or whether their digit sums match. The odd one fails the shared property. Knowing squares up to 30 and primes up to 100 makes this much faster.

Which exams ask Odd One Out MCQs?

Classification questions appear in MDCAT, NTS and GAT tests, ISSB intelligence tests and forces initial tests in Pakistan, SSC CGL, SSC CHSL, IBPS and RRB exams in India, and the BCS mental ability paper in Bangladesh.

Why is a dolphin the odd one out among fish?

A dolphin is a mammal: it breathes air through lungs, is warm-blooded and gives birth to live young that it feeds on milk. Tuna, salmon and sharks are fish that breathe through gills, so the dolphin does not belong.

Last reviewed October 2026