Kakuro: sum 21 in 4 cells
A sum of 21 in 4 cells can be made 11 ways.
| Combination | Digit set |
|---|---|
| 1 + 3 + 8 + 9 | 1389 |
| 1 + 4 + 7 + 9 | 1479 |
| 1 + 5 + 6 + 9 | 1569 |
| 1 + 5 + 7 + 8 | 1578 |
| 2 + 3 + 7 + 9 | 2379 |
| 2 + 4 + 6 + 9 | 2469 |
| 2 + 4 + 7 + 8 | 2478 |
| 2 + 5 + 6 + 8 | 2568 |
| 3 + 4 + 5 + 9 | 3459 |
| 3 + 4 + 6 + 8 | 3468 |
| 3 + 5 + 6 + 7 | 3567 |
What this tells you
- There are 11 possibilities, so this clue alone does not decide the digits. Use crossing runs and any known cells to eliminate combinations.
- Every digit from 1 to 9 appears in at least one combination, so there is nothing to exclude outright.
Related sums
The digits left out of each combination form a combination for the mirror run: sum 24 in 5 cells (page).