NVR: odd one out with figures

Watch it happen

Hunt the odd one out

Four figures, labelled A to D. Three of them follow one shared rule. One breaks it. Compare them two at a time.

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The idea

Four figures look similar, but three of them share a rule and one breaks it. Your job is to find the rule, not just the figure that looks strangest. A figure can look different in a small way and still follow the rule, so guessing by appearance is risky.

Check features in a fixed order, one at a time: shape, number of sides, shading, size, direction, and numbers of dots, lines or parts. For each feature, ask whether three figures agree and one disagrees. Counting is powerful here: a link like 'dots equal sides' only appears when you count both things in every figure.

When you think you have found the odd one, state the rule in a full sentence: 'The others all have...' Then test that sentence against all four figures, one by one. If it fails for any of the three, it is not the rule, so return to your feature list and try the next feature. Never stop at the first difference you spot: it might be a decoy that splits the figures two and two, which can never give one odd one out.

Worked example

Four figures are shown, labelled A to D. Three of them follow one shared rule; one breaks it. Which figure is the odd one out?

1. Figure A is a light grey hexagon — it has 6 sides.

   

2. Figure B is a light grey triangle — it has 3 sides.

   

3. Figure C is a light grey square — it has 4 sides.

   

4. Figure D is a light grey star — it has 10 sides.

   

5. Compare the four notes: three figures share one rule and one breaks it — the odd one out is figure B.

   

Answer: B — Three of the figures follow the same rule: they all have an even number of sides. Figure B is the odd one out because it has 3 sides, an odd number. The other figures differ in size, shading or position, but those differences do not break the rule.

Try one yourself

Four more figures, labelled A to D. Which is the odd one out, and why?

Watch out

• Picking the figure that merely looks different instead of the one that breaks a rule the other three share.
• Stopping at a difference that splits the figures two against two — that cannot leave a single odd one out.
• Forgetting to test your rule on all four figures; a true rule fits three exactly and fails only one.