You are looking for missing digits in blocks, rows, or columns, but are "stuck". For example, when it seems to fit in the cell and 1, and 2, and even 7. In this case, we recommend that you use the method of notes - indicating the numbers that hypothetically might fit in the cell.
If you solve Sudoku on paper, you can make notes in pencil and erase them afterwards. Or, you can write with a pen, barely pressing. As an option - put small numbers in the corner of the cell, so that in the future they do not distract.
If you solve Sudoku on our website or mobile app, you can make notes using a special mode that is activated by the "pencil" button. Let's look at an example of using note mode - take a close look at the image below:
- which values are already in the central 3x3 block: 2, 4, 6, 3 and 7;
- which numbers are missing in the block: 1, 5, 8, and 9
- turn on the note mode and write: 1, 5, 8 and 9 in the empty cells (see the picture below);
- which numbers are in the row (3, 6, 7, 4);
- which numbers are in the column (8, 9, 2, 3, 1).
By method of elimination, we find that in the intersection cell (indicated by the orange frame) the only possible digit is a five. So we turn off the note mode and write in the cell the number 5.