Mathematicians: You must have at least 17 clues to solve Sudoku

A recent mathematics study showed that you have to have at least 17 clues on a Sudoku grid in order for the puzzle to be solvable. You could make the game easier, by adding more clues. But if there are fewer than 17 clues, then the game becomes impossible to solve. In this video, mathematician James Grime explains how the researchers figured this out.

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Via Grrlscientist and The Guardian