Naked triple
HardThree cells of the same row, column or box that, between them, can only hold the same three digits take those three digits. None of the three can then go anywhere else in that row, column or box. Each cell doesn’t need all three: 12, 23 and 13 make a triple too.
How to spot it
- With notes, look for cells of one unit with two or three candidates.
- Find three of them whose candidates, put together, are only three digits.
- Remove those three digits from every other cell of the unit.
Why it works
Three cells need three different digits, and only three digits are available to them, so they use up all three. Any other cell of the unit that held one of them would leave a triple cell empty.
Example
2
9
5
6
8
6
9
8
5
2
3
3
8
5
6
2
9
7
8
9
6
6
9
8
5
9
6
8
3
9
8
4
2
6
5
6
8
9
1
4
2
1
6
8
9
Look at box 5.
Common mistakes
- Counting a cell that has a fourth candidate: then the four cells’ digits are four, not three.
- Removing the digits from cells outside the unit the three cells share.