Calendar Magic

With the second button on the left reading "Set", drag the cursor inside the table and select a square array of dates. Once you are satisfied with your selection, click the button. The label will change to "Play". While playing pick up dates inside the select area. One in each row and in each column. Sum up selected dates. The sum that also appears in the lower right corner does not depend on selection of dates inside the square but only on the square itself. See if you can verify or even prove this.


This applet requires Sun's Java VM 2 which your browser may perceive as a popup. Which it is not. If you want to see the applet work, visit Sun's website at, download and install Java VM and enjoy the applet.

What if applet does not run?


There is a combinatorial game - the Date game - that can be played on an a yearly wall calendar or practiced by playing with the computer.

Related material

  • An Arithmetic Magic Trick
  • Bachet's Magic Trick
  • Gergonne's Magic Trick
  • Hummer's Mind Reader
  • Magic in Square
  • Math Telepathy
  • Number Guessing Game. All by Computer
  • Barcode Magic
  • Arithmetic magic matrix
  • Two Numbers Guessing Game
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