Rule
A new hidden rule every day. Work out what it is by testing your guesses.
Puzzle #—
There is a hidden rule about three numbers
Test any three numbers from 1 to 99 and you will be told whether they follow the rule. Test as many as you like — then prove you have it.
Your tests (0)
Prove it
Say whether each of these follows the rule. Get all six right and the puzzle is yours.
There is a hidden rule about three numbers. You are shown two combinations that follow it and one that does not — and that is all you get for free. From there you find the rule by testing combinations of your own, as many as you like, each one answered immediately with a yes or a no.
When you are confident, you do not type the rule out. You prove you have it by sorting six fresh combinations correctly. That way there is never an argument about phrasing — either you can apply the rule or you cannot.
The trap almost everyone falls into
This puzzle is built on a famous experiment by the psychologist Peter Wason. He gave people the sequence 2, 4, 6 and asked them to work out the rule behind it. Almost everyone guessed something like “goes up in twos”, and then tested 8, 10, 12. It passed. So they tried 20, 22, 24. That passed too. Confident now, they announced their answer — and were wrong. The actual rule was simply “any three numbers that increase”.
The mistake was not the hypothesis. It was that every test they chose was one they expected to pass, and a test you expect to pass cannot teach you anything when it does. The people who solved it quickly were the ones who deliberately tried something they thought would fail — 1, 2, 100, or 5, 4, 3 — because a surprise is the only result that carries information.
So the useful instinct here is an uncomfortable one: once you have a theory, go looking for the combination that would prove you wrong.
Controls
| Three numbers + Test | Asks whether that combination follows the hidden rule. |
|---|---|
| I know the rule | Opens the six-question check that proves you have it. |
| Enter | Submits the numbers you have typed. |
Questions
How do I actually win?
You never type the rule out. Instead you prove you know it by correctly sorting six fresh combinations into ones that follow the rule and ones that break it. Get all six right and the puzzle is solved.
Is there a limit on how many combinations I can test?
No. Test as many as you like — your score is simply how few you needed, so there is no way to lose by being thorough.
Is it the same puzzle for everyone?
Yes. The rule is chosen from the date, so everybody in the world gets the same one on the same day, and a new one arrives at your local midnight.
Why do I keep getting it wrong when I felt certain?
Because of how people naturally test ideas. Almost everyone tries examples they expect to pass, which can only ever agree with them. The fastest solvers deliberately test combinations they expect to fail, because only a surprise actually tells you something new.
Do I need to know any maths?
No. The rules only ever involve things like size order, odd and even, or repeated numbers. There is no arithmetic you cannot do in your head, and no vocabulary or trivia at all.