Techniques · killer sudoku

45-Rule (Box/Row/Column)

Every row, column and box adds up to 45. Subtract the cages that lie wholly inside it, and the one cell left over must make up the difference.

In the walkthroughs, every 45-Rule (Box/Row/Column) step shades the cells of the pattern and names the cell and digit it proves, so you can see the move on the grid rather than read about it. Press “Skip to next hard step” to jump straight to it.

None of the walkthroughs published so far needs this one; it is here for completeness.

Where it sits

See the whole ladder on hard killer sudoku techniques, or look a puzzle up by number under solutions.