A re-trap is a different question that sets the same trap. Not the question your child got wrong — a new one, chosen because it offers the same tempting wrong answer, mixed in with others so they cannot see it coming, and booked for about a week after the mistake was worked through. It is the mechanism the Maths Challenge room names as the thing that actually shifts a mistake.
The product puts it in one sentence on the mistake page: "Pi walks the ladder to a worked twin, then you redo yours. A re-trap is booked for a week later — that's what moves it, not the chat."
Why not just redo the question?
Redoing the original question tests recall of an answer. Your child sat with that question ten minutes ago; of course they can do it now. It proves nothing about whether the underlying trap would still catch them.
So the re-trap changes the question and keeps the trap. When one arrives, it says so:
New question. Same trap. This isn't the one you got wrong — it's a different question that offers the same tempting answer.
That framing is deliberate. Your child knows a trap is in there somewhere and still has to spot it, which is much closer to what happens in a real 25-question paper than any amount of re-reading.
Choosing what goes in
From any mistake in the clinic there is a Practise this one option. Your child picks the scope:
- Everything — every mistake currently on the list.
- Just the ×4s — only the ones with the heaviest counts.
They can also filter by Topic. Before starting, they get an honest estimate of the size of the thing:
6 questions · about 9 minutes · mixed up on purpose
"Mixed up on purpose" is doing real work in that line. If all six questions were the same kind, your child would solve the first one and pattern-match the rest without ever recognising the trap. Interleaving them removes that shortcut.
There is also "I'm not sure" as an offered answer. It is not a wasted turn — it is a truthful one, and a child who can say it is easier to teach than one who guesses to look busy.
The four outcomes
Every question in a re-trap ends in one of four ways, and the product names all four in plain words.
| Outcome | What the product says | What it means |
|---|---|---|
| Clean | "Clean — the trap was there and you walked past it." | The trap was set and it did not work. Real evidence the mistake is settling. |
| Caught again | "It caught you again. That's evidence, not a verdict." | Still live. The count grows and the entry stays active. |
| Wrong, but not that trap | — | Wrong for a different reason. This one does not count against the mistake being practised. |
| Blank | "Left blank — honest, and it moves nothing." | No dishonour, and no information either. |
At the end there is a summary in the same register: "2 clean re-traps · 1 caught you again · 0 left blank".
Notice what is absent. There is no percentage, no readiness figure, no verdict about how ready your child is for the real thing. A re-trap reports what happened and stops there — a decision we explain in why we don't tell you it was a Gold.
The third outcome is the subtle one. "Wrong, but not that trap" keeps the accounting clean: your child can get a re-trap question wrong for an unrelated reason without that being logged as the original mistake recurring. Without that distinction the count would drift and stop meaning anything.
The blank is a real answer
"Left blank — honest, and it moves nothing." is one of the more carefully judged lines in the room. It refuses to praise a blank and refuses to punish it. A blank is a truthful report that your child did not know, and truthful reports are what the clinic runs on — but it also does not advance the mistake in either direction, and saying so avoids the impression that leaving things blank is a way of making the list shorter. There is more on this in blank, wrong, or a guess.
When the trap runs out
A trap can be exhausted. When your child has met every question in the bank that sets it, the room says so: "You've met every question that sets this trap. It'll keep showing up in papers."
That second sentence is the honest half. Running out of re-trap questions is not the same as the mistake being cured — it means the drill has nothing new to offer, and future evidence will come from full papers instead.
Where the re-trap sits in a week
The intended shape is small and unhurried. A mistake appears in the clinic. Your child takes it to Professor Pi, who walks the hint ladder to a worked twin — a fully worked similar problem — and then asks them to redo their own; Pi never hands over the answer to their own question. That is covered in taking a mistake to Professor Pi. Then, roughly a week on, the re-trap arrives and tells you whether any of it took.
None of this needs an hour. Six questions and about nine minutes, once a week, against mistakes your child's own papers produced — that is a whole term of Maths Challenge practice with nothing wasted on topics they were already fine with.
FAQ
Is a re-trap just the same question again?
No — that is the whole point of the name. The product says it plainly: new question, same trap. This is not the one your child got wrong; it is a different question that offers the same tempting answer. Redoing the original would test whether they remember the answer, not whether the trap still works on them.
Why wait about a week before the re-trap?
Because a re-trap asked five minutes after the explanation only shows that your child was listening five minutes ago. The gap is what turns it into evidence. The product books the re-trap for about a week later and says outright that this is what moves a mistake, not the chat.
What if my child gets caught by the same trap again?
The product's own words are: it caught you again, that's evidence, not a verdict. The mistake stays live with more weight behind it, which is exactly the information practice is meant to produce. Nothing about it is scored or reported as a failure.
Related reading
- Practice Organised by the Mistake
- Taking a Mistake to Professor Pi
- The UK Junior Mathematical Challenge
Duke Harewood built aitutors.me for his own KS3-aged daughter. The re-trap exists because she could explain a mistake perfectly on Tuesday and walk straight back into it the following week. Updated 10 September 2026.