- Column 1: 3, 4, and 7 fit only in the highlighted cells.
- So these cells are taken by 3, 4, and 7, one each.
- So these cells can hold no other numbers.
Hidden Triple in sudoku
A Hidden Triple is three numbers that, within one row, column or box, are noted only in the same three cells. A number need not appear in all three. Those cells must take the three numbers, so every other note in them can be removed.
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How to spot it
Count, for each number, the cells of a row, column or box where it is noted. Look for three numbers whose cells, put together, are just three cells. It is one of the harder patterns to see, because the cells are usually full of other notes.
Why it works
Three numbers need three cells of the unit, and only those three are open to them. The three cells are spoken for, so nothing else can go in them.
On a real puzzle
This is Hidden Triple 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 Triple. 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.