Naked triple
Three cells in one unit whose candidates together are only three digits use up all three.
The idea
A naked triple is the naked pair with one more cell. Three cells in the same unit, whose notes together contain only three digits, say 1, 5 and 8. Each cell doesn't need all three: 1-5, 5-8 and 1-8 is a triple too.
Those three cells will take 1, 5 and 8 between them, so no other cell in the unit can hold any of them.
How to spot it
- Look for cells with two or three notes in the same unit, and check whether three of them stay within three digits.
- Easiest to find in units with four to six empty cells.
Worked example
Naked triple on a real puzzle
From our expert puzzle #789 (27 clues), after 12 earlier steps of our solver. Gold cells make the pattern; red notes are the ones it rules out.
How often our puzzles need it
Our solver works like a careful player: it always uses the easiest technique that still makes progress. Counting the puzzles where it had to use naked triple at least once:
- 338 of our 1000 expert puzzles
- 57 of our 1000 master puzzles
The easiest level that can need it is expert Sudoku.