On Pi Day magician Brian Brushwood and mathematician James Grime performed the biggest scale Twitter-based mind reading stunt ever conceived. You too can play this interactive game with this tool.

You'll be ask to multiply random single digit numbers. Use a pocket calculator to perform some multiplications: just press any digit from 1 to 9, then press the multiplication button, followed by another digit from 1 to 9, and go on multiplying the result as many times as you like, until you reach a 7 or 8 digits number (between 1,000,000 and 99,999,999).

Write down the result of your calculations, then circle any digit of your number: that will be your secret number. Now scramble the remaining digits and write them in the box below, then press "Read my mind"

This tool will read the secret number in your mind.

Example

By pressing these buttons on a calculator: 3 × 5 × 3 × 5 × 5 × 5 × 7 × 9 × 9 I get this result: 3189375

I choose the digit "7" as my secret number and I remove it, getting: 318935

Now I scramble the digits, getting 133598

After having written it in the textbox above, the tool is able to discover the secret number "7", reading it in my mind.

Here is my Twitter contribution to the brilliant stunt.

How does it work?

At the Mathematical Forecasting Initiative, we respect magicians' secrecy, so we invite you to follow the authors of this stunt in the special episode of Scam School in which they will reveal how the trick does work.

Credits

The man behind this mathematical game is James Grime: this tool is a homage to his genius!

The creator of this software is not involved in "Pi Day Twitter Mind Reading" event: the algorithm running here is the result of a reverse engineering work, starting from Grime's brilliant idea.