No. XII.—A CENTURY OF CELLS
Here is the solution of the ingenious Magic Square of 100 cells with 36 cells unfilled. The rows, columns, and diagonals all add up to 505.
| 91 | 2 | 3 | 97 | 6 | 95 | 94 | 8 | 9 | 100 |
| 20 | 82 | 83 | 17 | 16 | 15 | 14 | 88 | 89 | 81 |
| 21 | 72 | 73 | 74 | 25 | 26 | 27 | 78 | 79 | 30 |
| 60 | 39 | 38 | 64 | 66 | 65 | 67 | 33 | 32 | 41 |
| 50 | 49 | 48 | 57 | 55 | 56 | 54 | 43 | 42 | 51 |
| 61 | 59 | 58 | 47 | 45 | 46 | 44 | 53 | 52 | 40 |
| 31 | 69 | 68 | 34 | 35 | 36 | 37 | 63 | 62 | 70 |
| 80 | 22 | 23 | 24 | 75 | 76 | 77 | 28 | 29 | 71 |
| 90 | 12 | 13 | 87 | 86 | 85 | 84 | 18 | 19 | 11 |
| 1 | 99 | 98 | 4 | 96 | 5 | 7 | 93 | 92 | 10 |
Notice that the top and bottom rows contain all the numbers from 1 to 10 and from 91 to 100; the two rows next to these range from 11 to 20 and from 81 to 90; the two next from 21 to 30 and from 71 to 80; the two next from 31 to 39 and 60 to 70, excluding 61, but including 41; and the two central rows the numbers run from 42 to 59, with 40 and 61.
No. XXIII.—TWIN PUZZLE SQUARES
The following diagram shows how the twin Magic Squares are evolved from our diagram:—
| 1 | 5 | 6 | 2 | 3 | 7 | |
| 2 | 6 | 7 | 3 | 4 | 8 | |
| 3 | 7 | 8 | 4 | 5 | 9 | |
The sums of the corresponding rows in each square are now equal, and the sums of the squares of the corresponding cells of these rows are equal. The sums of the four diagonals are also equal, and the sum of the squares of the cells in corresponding diagonals are equal. The sum of any two numbers symmetrically placed with respect to the connecting link between the 7 and the 3 is always 10.