Hidden Pair
A hidden pair is two digits that, in one row, column or box, fit in only the same two cells. Those cells must hold those two digits, so anything else in them can go.
Ninesmith Sudoku ·
In short
- In one house, find two digits that each have only two possible cells, and the same two.
- Those two cells take those two digits, one each.
- Strike every other candidate from those two cells.
An example
Before the pair, the cell at row 7, column 2 shows five candidates and looks hopeless. After it, both cells are down to 3 and 9: a naked pair. That is why the hidden pair is hidden: the cells look crowded, and only the digits give it away.
How to spot one
- Work digit by digit inside one house: where can each missing digit go?
- Note the digits with exactly two places. If two of them share the same two cells, that's the pair.
- Rows and columns work the same as boxes.
Hidden triples
Three digits that fit in only the same three cells of a house make a hidden triple: every other candidate comes out of those cells. As with naked triples, each cell needn't hold all three.
Hidden pair or naked pair?
A naked pair is two cells with only two candidates; it clears the rest of the house. A hidden pair is two digits with only two cells; it clears the rest of those cells. In a house, one often comes with the other on the remaining cells, and you can use whichever you see first.
Questions
What is a hidden pair in Sudoku?
Two digits that can only go in the same two cells of a row, column or box. All other candidates in those two cells can be removed.
Is a hidden pair harder than a naked pair?
It is harder to see, because the two cells still show other candidates. The logic is just as simple.
Next: Locked Candidates · all techniques
Get unstuck with the Smith
Ninesmith Sudoku is a calm Sudoku app for iPhone. When you're stuck, the Smith names the technique, hidden pairs included, and shows where to look before anything goes in. The Pattern Trainer drills naked pairs and both kinds of triple.
Get the appFree to play. No ads in any tier.