3x3 Magic Number Square

This is a maths puzzle based on a very ancient Chinese number square called Lo Shu. According to legend, 4000 years ago the Chinese emperor Fu Hsi found a turtle in the river Lo. On the turtles back were 9 bumps on its shell arranged as a grid of three rows by three columns. In each bump there were a number of marks corresponding to the numbers 1 to 9.

Now the reason the square is magic, is that if you add up the numbers in each bump in each row you would get the number 15. The same is true if you add all the numbers in each column and each diagonal! The other important thing is that each number from 1 to 9 only appears one time.

So, the object of this puzzle is to work out the numbers in the Lo Shu when you only have a few numbers to get you started...

When the game is started by pressing the green button, you will see the main game screen. This has the 3x3 Lo Shu number grid containing the starting numbers in black. There are also two buttons : a "clear" button which restarts the game, and a "check" button that you can click to see if you have got all the numbers right.

To add a number to any of the squares, drag and drop one of the coloured numbers below the number grid into one of the circles. You cannot replace the starting numbers (in black) and you will get a warning sound if you try to. To change a number, just drag and drop another number on top.

When you have filled in all the numbers, click the "check" button to see if you are right...

This puzzle is also available as a print-out using PDF files.

The puzzle can be found here [PDF file 106 kB]

The solution can be found here [PDF file 108 kB]