Start with the idea
Start with three numbers in one row, column, or 3x3 box. In this example, 2, 5, and 8 can only fit in three cells of the bottom-left box. Those cells are reserved for those numbers, so their extra notes can be erased.
Look for this pattern
Look for a small group of squares in the same row, column, or box. The group can reserve a matching set of numbers.
This empty board keeps the puzzle numbers out of the way so the pattern is easier to see.
Example
3
7
6
1
9
5
9
6
6
3
4
8
3
1
2
6
2
5
8
9
6
1
4
9
2
4
5
1
9
1
3
7
5
7
8
Look here firstLook inside the bottom-left 3x3 box and focus on 2, 5, and 8. Those numbers are limited to three cells.
This technique cleans up candidates inside the three hidden cells.
Keep 2, 5, and 8 in those cells, and erase the other notes from those cells.
- Scan one row, column, or 3x3 box by number.
- Find three numbers that are limited to the same three cells.
- Keep those numbers there and remove the extra notes.
2, 5, and 8 to keepextra notes to erase
When to look for it
Use it when a row, column, or box's note lists are cluttered but three digits keep landing in the same three cells.
How to use it
- Choose a row, column, or box.
- Track note locations for three digits.
- If those digits appear only in the same three cells, keep those digits and clear the extras there.
Common mistakes
- A hidden triple does not usually eliminate notes from other cells.
- It often turns into singles or naked pairs after cleanup.