Math games Rules for resolving a Sudoku
Resolutive Methodologies • The aim of the game is to fill the white boxes with numbers from 1 to 9, so that in every row, in each column and in each square region with bold edges, all the numbers from 1 to 9 are present without repetition. But this is just the rule. Actually to solve the game we need logic and inventiveness.
Resolutive Methodologies
Reduce the playing field to three horizontal lines at a time, starting from those where there are more numbers. In the example below I started from the first three lines, those with gray background. Notice that the number 7 is already in three squares and in all three lines, so you can’t add others any more. The number 1 instead is present only in 2 squares, then it is missing in the third square of the the second row. So the 1 will be there: in the third box in the second row.
So the 1 will be there: in the third box in the second row. However, there are two free positions: the one under the 6 and the one under the 5. The 1 can’t be under 6 because in the same column there is already 1, so it must be under 5. As soon as we placed the 1, we can fix the last vertical band, as shown. We can see that the 1 is in every square and in every column, so we do not need it any more. The 8 instead is missing in the first column and in the last square. It can only stay in one place in the first gray column above 1 and under 4.
• In the seventh column, indicates with the orange line, only two numbers are missing, it is easy to understand what they are, 2 and 5. Let's mark them in pencil and try to figure out which one should be excluded. In the box at the top right is already present the 5, so in the blue sky box there can’t be 5, gate 5 and only remains 2.
• In the box at the top right is already present the 5, so in the blue sky box ,there can’t be 5, we delete the 5 and only the number 2 remains.
SUDOKU
Thank you all for your attention The Italian team