Odd One Out / Classification

Find the rule that three share. The odd one breaks it. Check primes, squares, cubes, even/odd, vowels, letter gaps.

Start with this

Apple, mango, carrot, banana: carrot is the odd one because it is a vegetable. Find the rule three of them share.

Classification is quick marks: find a property that three options share and one does not.

Numbers and letters

Numbers: test prime or not, square or cube, even or odd, digit sum, divisible by something.

Letters: convert to positions and test gaps, vowels, opposite pairs.

Worked example

Find the odd one: 27, 64, 125, 144, 216

1. 27 = 3³, 64 = 4³, 125 = 5³, 216 = 6³.
   Why: Cubes.
2. 144 = 12² is not a cube.

Answer: 144

Worked example

Find the odd one: BD, FH, JL, NQ

1. BD: gap 2. FH: 2. JL: 2. NQ: 3.
   Why: Letter positions.
2. NQ.

Answer: NQ

Shortcut: Letter-gap check

Use it when: Letter groups.

1. Convert to positions and look at the gaps.

Letter-gap check: try it

ACE, BDF, GIK, LNQ

1. Gaps 2,2 in the first three; LNQ is 2,3.

Answer: LNQ

Your turn medium

Odd one: AZ, BY, CX, DV

1. Reverse pairs sum to 27: D(4)+W(23). DV is 4+22.

Answer: DV

Recap

• test prime, square, cube, parity and digit sum
• turn letters into positions and compare gaps

Now practise

5 questions with full solutions.

Open practice Back to the lesson