Naked triple in Sudoku

How it works

Three cells must hold three different digits. If the only candidates in those cells, taken together, are three digits, then those digits fill the three cells, in some order, and cannot appear anywhere else in the unit.

Here is the catch that confuses people: each cell does not need all three digits. A triple on 4, 5 and 8 could be three cells with the notes 45, 58 and 48. No cell has all three, but together they hold exactly three digits, and that is enough.

1. In a unit, look for cells with two or three notes.
2. Find three of them whose notes, combined, are exactly three digits.
3. Remove those three digits from every other cell of the unit.

A real example

The three blue cells share three digits between them. The red candidates in the rest of the unit are those same digits and are removed.

How to spot them

Start from a cell with two notes and look for partners in its unit whose notes overlap with it and add only one new digit. Three cells and three digits is the test. If the count comes to four digits, it is not a triple. Naked triples are most common in units with five or six empty cells.

Triples and pairs

Any unit splits into two groups: the cells of the triple and the rest. If a row has five empty cells and three of them form a naked triple, the other two form a hidden pair. They are the same deduction, and you will usually find the smaller group first. This is why Sudoku Clan asks for triples only in Fiendish puzzles, its top level.