You can fill a 3×3 magic square using an algorithm or by intuition. The sum of rows, columns, and diagonals is 15.
The center is 5 (it appears in four sums).
Since the number in the center is odd, and 15 is odd too, each pair of numbers on its side has same evenness.
All the pairs of numbers encircling the center sum to 10. There are four combinations: 1 + 9, 2 + 8, 3 + 7, and 4 + 6.
Fill the square by starting with a pair and checking the sums!
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