In box 6, R6C9 is the only cell that can contain 4. Place 4 there.
What to look for
Choose a missing digit and check every cell in a row, column or box. Look for a digit that has just one possible position, even if that cell has other candidates.
Why it works
The digit must appear somewhere in the house. If only one cell can contain it, it must go there.
Try it step by step
- Choose a digit missing from a row, column or box.
- Find every cell in that house where the digit is a candidate.
- If there is only one, fill in the digit there.
Try it on a real puzzle
Start with the highlighted step, then keep solving. Use "Apply hint" to make the suggested change, or enter your own digits and candidate notes. Use "Undo" to reverse your last change.
| C1 | C2 | C3 | C4 | C5 | C6 | C7 | C8 | C9 | |
|---|---|---|---|---|---|---|---|---|---|
| R1 | |||||||||
| R2 | |||||||||
| R3 | |||||||||
| R4 | |||||||||
| R5 | |||||||||
| R6 | |||||||||
| R7 | |||||||||
| R8 | |||||||||
| R9 |
Use the arrow keys to move, 1-9 to enter a digit and Backspace or Delete to clear a cell. To add or remove a candidate, press C and then 1-9.
Source puzzle number: 253929 · Play this puzzle from the start
A simple example
If only one cell in row 4 has candidate 7, that cell must be 7, even if it also has candidates 2, 6 and 8.
A house is a row, column or 3 × 3 box. A line is a row or column. Two cells "see" each other when they share a house. R1C3 means row 1, column 3. Boxes are numbered 1-9 from left to right and top to bottom. Braces such as {1, 2} show a cell's candidates, not confirmed digits.