Variant Sudoku

Kropki Sudoku Dots Explained in One Short Example

0:18 · Kropki dots · Variant Sudoku

A four-cell row with a white dot and a black dot shows the Kropki rules. 4 and 5 fit the white dot, 3 and 7 fail the black dot, and 3 and 6 pass because 6 is double 3.

Full lesson and practicePlay Kropki Sudoku

Transcript

  1. 0:02A white dot joins consecutive digits. A black dot joins digits where one is double the other.
  2. 0:064 and 5 are one apart, so they fit the white dot.
  3. 0:093 and 7 don’t fit the black dot: 7 isn’t double 3.
  4. 0:123 and 6 do: 6 is double 3.

The rule

Kropki sudoku adds small dots on the borders between cells. A white dot means the two digits are one apart, like 4 and 5. A black dot means one digit is double the other, like 3 and 6.

The dots cut each cell down to a handful of options. Check the last line of the rules too. If all dots are given, every pair without a dot is neither consecutive nor in a 1:2 ratio, so the blank borders carry clues as well.

Worth memorizing

  1. 5, 7 and 9 can never sit on a black dot.

    Their doubles are over 9 and their halves aren’t whole.

  2. 1 and 2 fit both colors

    they’re consecutive and one is double the other.

  3. Watch the last line of the rules.

    “All dots are given” means every pair without a dot is neither consecutive nor 1:2.

Practice kropki dots in the lesson

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