Naked Quad
Four cells in a run whose candidates combine to exactly four digits — eliminate those digits elsewhere in the run.
How it works
- 1The four highlighted cells between them use only the digits 1, 2, 3 and 4 — four cells, four digits.
- 2So all four are consumed inside that group, whatever order they end up in.
- 3Strike 2 and 4 from the last cell, leaving 9. Check it: 1 + 2 + 3 + 4 + 9 = 19.
- 4Quads are the last naked subset worth hunting — a five-cell version would leave too little of the run to eliminate from.
- Cells that establish the pattern
- Where the conclusion lands
- Digit ruled out