Two cells hold the same two candidates → erase that pair from the rest of the unit.
Technique 4 in the order the hint searches · difficulty Hard · up to pairs
Say two cells in the same row (or column, or box) are both down to exactly 3 and 8. Whichever one is the 3, the other is the 8. You don't know the order, but you do know those two cells take the 3 and the 8 between them.
Try pairing up the cells that have only two candidates
With notes on, pick out only the cells holding two candidates. If two of them sit in the same unit and carry identical digits, that's your pair. You place nothing, but the other cells in that unit get noticeably thinner.
How the hint says it
r5c2 and r5c4 can hold only 1 and 9. Those two digits take those two cells, so 1 and 9 come off the other cells in the same row.
Two cells use up both digits
In that unit, the home for the 1 and the home for the 4 are settled inside these two cells. If another cell in the line took the 1 or the 4, one of the pair would have nowhere left to go. So the 1 and 4 can be erased from the rest.
Puzzles that need pairs start at Hard. From here on, without notes written down, there is effectively nothing to see.
Puzzles that need this technique
Four puzzles with a spot where nothing moves until you use Naked Pair. Press a number to play it.
- Practice 1 ·
2-8871522 - Practice 2 ·
2-8307283 - Practice 3 ·
2-6614566 - Practice 4 ·
2-6050327