The illustration shows eighteen dominoes arranged in the form of a square so that the pips in every one of the six columns, six rows, and two long diagonals add up $13.$ This is the smallest summation possible with any selection of dominoes from an ordinary box of twenty-eight. The greatest possible summation is $23,$ and a solution for this number may be easily obtained by substituting for every number its complement to $6.$ Thus for every blank substitute a $6,$ for every $1$ a $5,$ for every $2$ a $4,$ for $3$ a $3,$ for $4$ a $2,$ for $5$ a $1,$ and for $6$ a blank. But the puzzle is to make a selection of eighteen dominoes and arrange them (in exactly the form shown below) so that the summations shall be $18$ in all the fourteen directions mentioned.
Solutions: 1
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