Derren Brown's Magic Square

The Effect:
A spectator gives you a random number and you're instantly able to create a magic square of numbers in which all rows, columns, diagonals and corners total his chosen number.




The Secrets:
This looks absolutely mind blowing when performed well but is technically easy to achieve.

The diagram below shows the basic framework for the square:

The numbers shown in the above square will always be present, whatever random number is chosen. You need to memorize the order and positions of those numbers. The grey squares A to D are where you will add additional numbers to complete the magic square.

If like me you have a terrible memory, write the basic framework of the magic square using very light pencil in the corner of your notepad or flip chart. It will be visible to you but not to your audience.

To begin, ask for a random number between 25 and 100. Let's say your spectator chooses the number 37.

Subtract 21 from the number given (in this example, we get 16) and put it in position A. Then add 1 to this number and put in position B. Add 1 again for the number in position C and finally 1 again for the number at D.

In our example, we finish up with the magic square shown below:

Look at the resulting square and you'll see that all rows and columns total 37 - the spectators chosen number. Also, both diagonals total 37. The numbers at each corner also total 37. And the four 2 by 2 squares at top left, top right, bottom left and bottom right also total 37 (e.g. 8, 11, 16 and 2; 17, 1, 7 and 12 etc.)!

Actually, there's more! Choose any 3 sided square and the numbers at each corner also total 37 (e.g. 8, 17, 3 and 9)!

Although this may seem like a simple concept, Derren Brown used a magic square effect as the encore for his 2004 UK tour and got a standing ovation!