Magic & Math with Cards

Lecture 46 · Performance

The 27-card trick

Choose the destination

Video in production

This lecture is still face down. Its script is written; filming and animation are under way.

Meanwhile, play the trick

What you will learn

Place a mentally selected card at any chosen position 1–27 using three column reports and a ternary collection code.

The trick in this lecture The 27-Card Trick Name a number from 1 to 27 and think of a card. After three deals, your card is at exactly that number. Play the trick

Before this lecture

Nothing. This lecture is a fine place to start.

In this lecture

An outline of the lecture, scene by scene, with the statements that appear on screen. It follows the draft script, so details may change in production.

  1. Choose target and report first column

    At the table
    • Choose target 1–27
    • Report column, not identity

  2. Complete adaptive deals

    At the table
    • Same card; three rounds

  3. Reveal at the chosen destination

    At the table
    • Reveal counts from 1

  4. Lock the collection convention

    • Zero-based p=3r+c

  5. Calculate one round

    • p' = 9k + floor(p/3)

  6. Encode the target

    • Target−1: ternary digits
    • Rounds read units first

  7. Diagnose handling and indexing

    • Preserve column order; assemble bottom-up

  8. Play and retrieve

    • Column identifies packet; code places packet

Companion interactive

Encode any target and route a hidden selected card there through column reports.

The trick page is this lecture’s companion: be the spectator, lift the curtain to step through why it works, try the challenge, then learn the handling.

Open The 27-Card Trick

Sources

How these sources were used
  • Numberphile, “Beautiful Card Trick (Matt Parker)”: 27-card target-position mechanism. Explicit all-face-up, row-order-preserving grid handling and ternary lookup are checked adaptations; not a transcript.