Naked pairs

If two cells in the same row, column or box both have exactly the same two candidates, those two numbers must fill those two cells, in some order. Nothing else in that row, column or box can be either number.

How to spot it

1. Find two cells in one unit with identical notes of exactly two numbers.
2. Those numbers belong to the pair, whichever way round.
3. Remove both numbers from every other cell in the unit.

A real example

In column 2, r5c2 and r7c2 can only be 2 or 8. Those two numbers must fill those two cells, so the rest of the column can’t hold either: r9c2 loses 2.

Tips

• The two cells must have exactly the same pair. Notes like 3/7 and 3/9 don’t form a pair.
• The same idea extends to naked triples, three cells that between them hold only three numbers.

Practice on Medium puzzles