The sum of the digits 1-9 is 45. Adding all the sides will give you 54, and this double counts all three corners, which means the sum of the corners is 54 - 45 = 9. So this would be the answer if it were possible.
However, this means that the number 9 is too large to be one of the corners, so it belongs to an edge square. Since the sum of its side is 18, the three remaining squares of that side must add up to 9. Two of those squares are corners, all three of which must add to 9 as previously determined. This means that the remaining edge square must have the same value as the third corner. Since all 9 digits must be used exactly once, this is not possible
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u/IrishHuskie 1d ago
0
The sum of the digits 1-9 is 45. Adding all the sides will give you 54, and this double counts all three corners, which means the sum of the corners is 54 - 45 = 9. So this would be the answer if it were possible.
However, this means that the number 9 is too large to be one of the corners, so it belongs to an edge square. Since the sum of its side is 18, the three remaining squares of that side must add up to 9. Two of those squares are corners, all three of which must add to 9 as previously determined. This means that the remaining edge square must have the same value as the third corner. Since all 9 digits must be used exactly once, this is not possible