Find Naked Pairs
Now you should look for matching pairs or trios of numbers in each column, row, and region. You have seen matching numbers before:
You can see the concept in the following illustration.
In this sample row from a sudoku grid you find number 1 and 8 in column 1. But at column 6 you also find the numbers 1 and 8. This matching pair is telling you that number 1 or 8 are the only choices for these two cells. If that is true, then neither of these numbers can be at any other cell in that row. So you can eliminate the 1 and 8 in any other cell of the row where they do not appear together.
As you can see, this immediately solves the cell at column 5. This rule can be applied to a row, column, or region.
Don’t hesitate to try to use this rule on any Sudoku puzzle that you attempt to solve. It may not always work but you want to get into the habit of applying a variety of solving strategies to any puzzle that you put your pencil to.
