Start with the idea
Start with two cells in the same row, column, or 3x3 box. In this example, two cells in row 5 can only be 2 or 8. Those two cells must use 2 and 8, so no other cell in that row can use those numbers.
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
5
3
7
6
1
9
5
9
8
6
6
3
2
8
2
4
8
3
2
8
1
2
8
7
6
6
1
9
5
8
7
Look here firstLook at row 5. Two cells contain only 2 and 8, so those two numbers are reserved for those two cells.
This technique reviews candidates instead of solving a square right away.
Remove 2 and 8 from the other cells in the row. Leave any other notes in those cells alone.
- Find two cells in the same row, column, or 3x3 box.
- Both cells contain only the same two notes.
- Remove those two notes from the other cells in that area.
2 and 8 pair2 and 8 notes to remove
When to look for it
Use it when two cells in a row, column, or box have exactly the same two possible numbers.
How to use it
- Find two cells in one row, column, or box with exactly the same two possible numbers.
- Confirm no extra notes are present in the pair cells.
- Remove those two notes from the other cells in the same row, column, or box.
Common mistakes
- The pair must be naked: exactly two notes in each pair cell.
- Removals happen only in the same row, column, or box.