Sudoku techniques · Hard
Naked Triple in Sudoku
A Naked Triple is three cells in the same unit whose candidates, pooled together, cover only three numbers. Those three numbers must fill those three cells, so the rest of the unit loses them. Crucially, the individual cells do not each need all three candidates.
Why it works
Three cells in the same row, column, or box whose candidates together cover only three numbers keep those numbers for themselves.
How to spot it
This is the pattern beginners look for wrongly. You are not hunting for three identical cells; you are hunting for three cells whose combined candidates total three numbers.
- Valid shapes include 123/123/123, 123/12/23 and 12/23/13. Any mix works as long as the union is three numbers.
- Start from two bivalue cells that overlap, then look for a third cell that adds at most one new number.
- A cell with four candidates can never join a triple.
Builds on
Worked example
These are the app's own lesson boards. Step through them the same way a hint does.
- 1
In this row, the candidates in these three cells are limited to 1, 3, 7.
- 2
These three cells together must contain 1, 3, 7, so we can remove the marked candidates from the other cells in this row.
- 3
Done! We've cleaned up the extra candidates and the board is simpler now.