Naked Pair
Two cells in a house showing the identical two candidates. Those digits are reserved for those cells and can be cleared from the rest of the house.
Two cells in this row both show only candidates 4 and 7.
How to spot it
- 1Find two cells in one house with the same two candidates, e.g. {4,7}.
- 2They must hold 4 and 7 between them.
- 3Remove 4 and 7 from every other cell of the house.
When to use
Once you're keeping candidate notes. Naked pairs are easy to spot and often trigger a single.
Common mistake
Treating cells as a pair when one carries a third candidate — then it isn't a naked pair.
Worked Example
Two cells in the same house — say a row — both show exactly the same two candidates, like {4, 7}. Between them, those two cells have to hold a 4 and a 7, in one order or the other; there's no third option for either cell.
That means no other cell in the row can be a 4 or a 7 either, since both digits are already spoken for. Any 4s or 7s pencilled into the rest of the row can be erased. Naked pairs are easy to spot once you're keeping candidate notes, and clearing them out frequently leaves some other cell in the row down to a single candidate.