Three-cover position trace
Track a known hidden card through three visible swaps of its closed container.
Adult planning suggestion: about 4–6 · Observation & recall · Logic & rule checking · Cooperation & communication
- Players
- 4–5 with an adult
- Time
- 8–12 minutes
- Materials and quantities
- Per station: three large identical opaque folded-paper pockets, one large red card, fixed position labels A/B/C and an optional trace.
30 children: six groups of five, but only adult-supervised stations operate simultaneously; others practise the large position diagram.
Prepare
Fix A,B,C labels to the table from left to right; they name positions, not moving pockets. Let everyone see the red card placed inside the pocket at A. Close all three pockets identically. They are large, adult-prepared and never used for money, prizes or a surprise object.
Play
Adult exchanges the complete closed pockets at two named positions, moving slowly and without hiding the hands. Wait for everyone to say or point to the tracked position. Use exactly these swaps: A with B, then B with C, then A with B. The target card travels inside its pocket.
Example
Start A. After A↔B the target is at B. After B↔C it is at C. The last A↔B does not touch C, so it remains at C. The printed position labels do not move, even when pockets do.
Finish
Ask for the final location, then open C to check. If the target slipped out or an exchange was obscured, reset and replay rather than declaring a child wrong. Rotate the explaining role or stop after one clear three-swap run; no rapid shuffling or elimination.
Adapt
First use only one swap or keep the target visible for a demonstration. Children may point, speak or have a partner record. Give a seated observer a clear view; never blindfold anyone or use the task to diagnose memory.
Aim: Track a known hidden card through three visible swaps of its closed container.
Practice within this activity: Updating position after a swap and recognising a swap that does not affect the target.
Adult observation: Ask why the final A/B swap leaves a target at C unchanged; accept a pointed explanation.
Mechanism and adaptation: Our version uses tracking a hidden identity through visible transpositions. Examples and print materials are separately written; the earliest inventor is not established here.
Reference checked 24 October 2026: Princeton University · Introduction to Programming in Java, Arrays — Computing background for exchanging values at two positions. The university code is not our children’s activity and does not establish its suitability or memory effects.
Goals describe observable activity choices, not measured long-term gains or institutional endorsement.
Free alternatives: Make three identical folded envelopes from scrap paper; an adult prepares them and checks the target stays inside.
Buying recommendations reserved; no purchase required.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Player fixed position mat
Positions remain on table. Adult uses three identical closed large paper pockets; the red card travels inside a pocket. Start by showing the red card at A.
A↔B, then B↔C, then A↔B. One slow visible swap at a time.
Optional target card and trace
| After | Target position |
|---|---|
| Start | ____ |
| A↔B | ____ |
| B↔C | ____ |
| A↔B | ____ |
Colour may be drawn by an adult; identity is shown before hiding. No money, blindfolds or speed tricks.
Teacher instructions and checked example · separate
30 children: six groups of five, but only adult-supervised stations operate simultaneously; others practise the large position diagram.
Per station: three large identical opaque folded-paper pockets, one large red card, fixed position labels A/B/C and an optional trace.
Make three identical folded envelopes from scrap paper; an adult prepares them and checks the target stays inside.
Print only the relevant player pages; keep this teacher page separate. Read the full web rules before leading. A helper may write or move pieces, and anyone may pause or pass. No classroom or physical-printer trial is claimed.
Trace A→B→C→C. The last swap touches only A and B. Reveal C after the prediction. If the card slipped or hands hid a move, reset rather than judge a wrong answer.