Hidden Triples
When three digits can only go in the same three cells of a unit, those cells reduce to that trio — every other candidate is cleared from them.
When to use it
Use when three digits are confined to the same three cells of a row, column or box, even if those cells also show other candidates.
Worked example
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Three digits — here 2, 5 and 8 — can only appear in these three cells of the row, hidden among other candidates.
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Since those digits must fill the three cells, every other candidate is removed from them.
Common mistakes
- Confusing it with a naked triple: a naked triple shows only the three digits; a hidden triple hides behind extra candidates.
- Requiring all three digits in every cell — each cell only needs some of them, as long as the trio appears nowhere else in the unit.
Frequently asked questions
What is a hidden triple in Sudoku?
Three digits that can only be placed in the same three cells of a unit. Those cells must hold the trio, so their other candidates can be removed.