Lesson 6 of 8
Naked triple
A naked triple is three cells in one unit whose candidates, taken together, come to exactly three digits. The three digits must fill those three cells between them, so none of them can appear anywhere else in the unit.
- Level
- Advanced
The pattern
Naked triple: what it does.
The three cells don't each need all three digits. {1, 2}, {2, 3} and {1, 3} is a triple, and so is {1, 2, 3} beside {1, 2} and {1, 3}. What matters is the total: three digits, three cells.
Because the digits are confined to those cells, the triple removes three digits from a whole row, column or box at once, which is why it so often breaks a puzzle open.
Example
Naked triple: a worked example.
Find three cells with three digits between them
Scan a unit for a group of three cells whose candidates together add up to exactly three digits. Two-mark cells are the easiest starting point.
Check nothing spills over
Every candidate in all three cells has to sit inside the same three digits. A fourth digit anywhere in the group makes it a larger set, not a triple, and the eliminations don't apply.
Remove the three digits from the unit
Delete all three digits from every other cell of the row, the column or the box.
Place what the removal uncovers
Clearing three digits from a unit often leaves another of its cells with a single candidate. Place everything that becomes certain before searching for the next pattern.
Every empty cell with its candidates written in. Nothing is marked yet.On this board, the pattern sits in r1c5, r5c5, and r8c5.It removes 5 and 7 from r6c5.
Video
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Spotting it
Naked triple: how to spot it.
- Units with several cells holding two or three candidates. The more of them there are, the more likely three of them share the same three digits.
- A cell showing three candidates is worth a second look: it may be the anchor of a triple with two two-mark cells beside it.
- Triples are rarer than pairs, so exhaust pairs and locked candidates first and treat a triple as the answer to a puzzle that has otherwise stalled.
Where it stops working
All three cells must share one unit, and their candidates must not reach beyond the same three digits. A cell with a fourth candidate breaks the group, and applying the eliminations anyway can remove the digit the puzzle actually needed. If a unit gives you a group that looks like a triple but one cell has an extra mark, you have found a larger set, not a triple.
Keep going
Related topics.
New to sudoku? The rules take two minutes to read, and the first-puzzle walkthrough covers the basics that come before any of these.
Practice it in Sudoku Mori.
Naked triple is lesson 6 in the game, with a worked example and three exercises, part of Sudoku Mori Full. Lesson puzzles are separate from your daily ones, and you can redo any lesson whenever you like.
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