Sudoku Grove
Killer Sudoku
Sudoku with sums. Fill the grid as usual; the dashed cages tell you what their squares add up to. Every puzzle has exactly one solution.
What are the rules of killer sudoku?
Killer sudoku has every rule of normal sudoku: each row, column and 3×3 box holds 1 to 9 once each. On top of that, the grid is split into cages, outlined with dashed lines. The small number in a cage's corner is the total of its squares, and a digit cannot repeat inside a cage. Most killer puzzles start with few or no digits given: the cage sums are the clues.
Which cage sums have only one answer?
Some totals can only be made one way. Spot these first: they tell you exactly which digits go in the cage, even before you know the order.
| Squares in cage | Total | Digits |
|---|---|---|
| 2 | 3 | 1 and 2 |
| 2 | 4 | 1 and 3 |
| 2 | 16 | 7 and 9 |
| 2 | 17 | 8 and 9 |
| 3 | 6 | 1, 2 and 3 |
| 3 | 7 | 1, 2 and 4 |
| 3 | 23 | 6, 8 and 9 |
| 3 | 24 | 7, 8 and 9 |
| 4 | 10 | 1, 2, 3 and 4 |
| 4 | 11 | 1, 2, 3 and 5 |
| 4 | 29 | 5, 7, 8 and 9 |
| 4 | 30 | 6, 7, 8 and 9 |
A single-square cage simply gives you its digit.
What is the rule of 45?
Every row, column and box adds up to 45 (1 + 2 + … + 9). If the cages inside a box cover all but one of its squares, add their totals and take the result from 45: the difference is the missing digit. The same works for a square sticking out of a box, and for groups of two or three rows or boxes (90, 135).
Tips
- Start with the unique sums in the table, and with single-square cages.
- Pencil in a cage's possible digits with Notes; then the normal sudoku rules cut them down.
- Use the rule of 45 on boxes where cages almost fit.
- Hints fill one square for you and point you to the step to look for.
New to sudoku itself? Start with how to play and the solving techniques, which all still apply.