The question contains pairs of words that are related to each other in a certain way. Three of the following four word pairs are alike as these have the same relationship and thus form a group. Which word pair is the one that DOES NOT belong to that group? (The words must be considered as meaningful English words and must not be related to each other based on the number of letters/number of consonants/vowels in the word.)

Correct — B. The relation in each pair is polygon → its true number of sides.

Pentagon - 5 sides ✓
Triangle - 3 sides ✓
Square - 4 sides ✓
Hexagon - 8 sides ✗, because a hexagon has 6 sides

The pair whose count is simply false is Hexagon - 8 sides → option (b)

Why the others are wrong

• (a)
  Pentagon - 5 sides — Pentagon - 5 sides is a true count, so this pair belongs to the group of correctly matched polygons.
• (c)
  Triangle - 3 sides — Triangle - 3 sides is a true count — three sides is the smallest number that closes a polygon.
• (d)
  Square - 4 sides — Square - 4 sides is a true count, matching the pattern set by the pentagon and the triangle.

Word-pair odd-one-out questions turn on the relation inside each pair, never on the words' spelling.

State the relation in words the moment you see the first pair: here, name of a polygon followed by how many sides it has. Then test the other three against that sentence.

The bracketed note rules out letter counts, consonant counts and vowel counts, so the only thing left to check is whether the fact is true.

Key facts

• A hexagon has six sides.
• An eight-sided polygon is an octagon.
• A pentagon has five sides, a square four, and a triangle three.

Common traps

• Confusing hexagon with octagon, the eight-sided figure
• Looking for a spelling or letter-count link, which the note rules out
• Assuming the odd pair must be the one with the largest number

No directly related past PYQ was found.