Platon Sudoku · Sudoku Study

Naked Single · Step-by-step example

Only one digit remains possible in a cell after the Sudoku rules are applied. Fill the cell with its sole remaining candidate.

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play

Recognize the pattern

Only one digit remains possible in a cell after the Sudoku rules are applied.

How to find it

Pick an empty cell and rule out digits already placed in its row, column, and box, or inspect its pencil marks.

What it allows

Fill the cell with its sole remaining candidate.

Avoid the mix-up

The cell need not be the last empty one in a region. A hidden single instead asks where one digit can go within a region.

Step-by-step example · Cell

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Check the row, column and box

R2C2: filled digits in its row, column and box rule out 1, 2, 3, 5, 6, 7, 8, 9, leaving only candidate 4.

R2C2. R2C2: filled digits in its row, column and box rule out 1, 2, 3, 5, 6, 7, 8, 9, leaving only candidate 4. Ruled out: 1, 2, 3, 5, 6, 7, 8, 9. Remaining: 4.

Step 2 · Conclusion

This cell must be 4.

This cell must be 4.

What it allows

This cell must be 4.

Naked Single · Fill the cell with its sole remaining candidate.

Practice

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play