Every row, column and diagonal adds to the same total.
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Some cells are filled and some are blank. Complete the grid so every row, every column and both diagonals add to the same magic constant, shown above the board.
There is no trial and error needed. Any line with one blank is immediately solvable — subtract the known values from the constant. Solve those, and new lines open up with one blank each. The whole puzzle unravels in a chain.
This version: Ten blanks on a sixteen-cell grid. Your best score is saved in this browser, so you can come back and try to beat it. Nothing is uploaded and no sign-up is needed.
For a normal n × n square using 1 to n², it is n(n²+1)/2. A 3 × 3 square gives 15, and a 4 × 4 gives 34.
Essentially yes. Every normal 3 × 3 magic square is the same square rotated or reflected — eight arrangements of one solution. The centre is always 5.
At least 2,000 years. The 3 × 3 square appears in Chinese texts as the Lo Shu, and they turn up independently in Indian, Arabic and European mathematics.