Kakuro: sum 4 in 2 cells
A sum of 4 in 2 cells has exactly one digit set: 1+3.
| Combination | Digit set |
|---|---|
| 1 + 3 | 13 |
What this tells you
- Unique. There is only one possibility, so as soon as you see this clue on a run of 2 cells you know the digits 1, 3 go in it. Only their order is open, and crossing runs usually decide that.
- Digits that can never appear: 2, 4, 5, 6, 7, 8, 9. You can remove them from every cell of the run.
Related sums
The digits left out of each combination form a combination for the mirror run: sum 41 in 7 cells.