Game technique · Sudoku
Naked Quads in Sudoku
Four cells whose combined candidates are exactly four digits reserve those digits in their unit.
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Four cells whose combined candidates are exactly four digits reserve those digits in their unit.
Example
Identify the four cells, then remove those four digits from the other cells in the same row, column, or box.
Key point
Four cells whose combined candidates are exactly four digits reserve those digits in their unit.