If a quadrilateral has all four sides equal but its angles are not all equal, it is a:

If a quadrilateral has all four sides equal but its angles are not all equal, it is a:
  1. Square
  2. Rectangle
  3. Rhombus (not a square)
  4. Trapezium

Solution

All sides equal $\Rightarrow$ rhombus. If the angles were also all equal it would be a square, so being a non-square rhombus is the answer.

Asked in: IMO

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