- Column 2: 7 and 8 fit only in the highlighted cells.
- So these cells are taken by 7 and 8, one each.
- So these cells can hold no other numbers.
Hidden Pair in sudoku
A Hidden Pair is two numbers that, within one row, column or box, are noted in the same two cells and nowhere else. Those two cells must take the two numbers, so every other note in them can be removed. What is left is a Naked Pair.
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How to spot it
Instead of looking at cells, count where each number can go in a row, column or box. When two numbers have the same two cells and no others, those cells are a Hidden Pair, however many other notes they carry.
Why it works
Each of the two numbers needs a cell in the unit, and only those two cells are open to them. Both cells are taken, so no third number can go in either.
On a real puzzle
This is Hidden Pair on its practice puzzle, at the first step that needs it. The game's hint explains the step like this:
Practice it
This Master puzzle calls for Hidden Pair. Fill in the singles first. When no number is obvious any more, look for the pattern, or ask for the hint: each game has one.