TECHNIQUE · INTERMEDIATE
Naked Pair — two cells claim two candidates
When two cells in the same row, column, or box share exactly the same two candidates, those digits can be removed from every other cell in that unit. It is the first technique to try when Singles stall.
The logic
If cell A and cell B are in the same unit and both contain only {a, b}, one must be a and the other b. No other cell in that unit can hold a or b.
How to find them
After writing full candidate lists, scan for cells with exactly two candidates. Check whether the same pair appears twice in one unit.
- Scan each row, column, and box for two-candidate cells.
- If the same pair appears twice in one unit, you have a Naked Pair.
- Remove those two digits from every other cell in the unit.
Naked vs. Hidden Pair
A Naked Pair looks at cells (two cells with the same candidates). A Hidden Pair looks at digits (two digits confined to the same two cells). The elimination is the same; the discovery angle differs.
Practice order
- Full candidatesWrite all possible digits in every empty cell.
- Find two-candidate cellsCollect cells with exactly two candidates per unit.
- Match pairsCheck if two cells in one unit share the same pair.
- EliminateRemove the paired digits from every other cell in that unit.
Walk through it step by step
Step 1 of 4
Start by reading row 1. The four right-hand cells are filled with 6, 7, 8, 9, so the five empty cells take candidates from {1, 2, 3, 4, 5}. Columns 3 and 4 are further restricted to {1, 2}.