Hidden Pair
Hidden Pair is a Number Place technique. When two specific numbers within a row, column, or block can only be placed in the same two cells, you can limit those cells’ candidates to just those two numbers.
How to Use Hidden Pair
Note the candidate numbers for each cell.
For each number, check which cells can hold it within a row, column, or block.
If two numbers can only go in the same two cells, that’s a Hidden Pair.
Remove all candidates except the pair’s two numbers from those two cells.
Example
Suppose a row has 6 empty cells. Checking candidates, you find ‘6’ can only go in two specific cells, and ‘8’ can also only go in those same two cells. Since ‘6’ and ‘8’ must occupy these two cells, you can eliminate all other candidates from those cells, leaving only ‘6, 8.’
Tips for Finding Hidden Pairs
Hidden Pairs are ‘hidden’ as the name suggests, making them hard to spot. Listing which cells each number can go in makes them easier to find. Specifically, if two numbers each appear as candidates in only 2 cells within an area, and those cells are the same, you’ve found a Hidden Pair.