The idea is that each digit has to appear in a column, row or square at least once.
The example below shows a 3*3 block with the values already written into it. Take a look at the rows and see what you can find vertically and horizontally. The eight in the 3x3 block can't be entered in three cells horizontally or vertically, as this would result in a duplicate.
So, we work out the "last remaining cell" by getting rid of the rest. In this example, you'll see it's on the left, vertically. You can go ahead and consider the block solved and move on to the others.
The method is based on excluding variants. The process is simple: we just throw away the cells until we find the right one. This method is pretty straightforward. It's used by beginners and experienced players alike, who often combine it with other techniques. Once you've got the hang of the 'last remaining cell' technique, you can move on to the next one.
Pick and choose from our selection of techniques, mix and match, and let your creativity soar as you tackle simple and hard Sudoku puzzles on our site!