Variant Sudoku

XV Sudoku Rules Explained in One Short Example

0:18 · XV · Variant Sudoku

A four-cell row with an X and a V shows the XV rule. 3 and 7 add up to 10 across the X, 2 and 5 fail the V because they make 7, and 1 and 4 make the 5 the V needs.

Full lesson and practicePlay XV Sudoku

Transcript

  1. 0:02Cells joined by an X sum to 10. Cells joined by a V sum to 5.
  2. 0:063 + 7 = 10 for the X.
  3. 0:092 + 5 = 7, so it can’t sit on a V.
  4. 0:121 + 4 = 5 for the V.

The rule

XV sudoku puts small letters on the borders between cells. Two cells joined by an X add up to 10, and two cells joined by a V add up to 5. Normal sudoku rules still apply.

Each mark allows only a few digit pairs, so one placed digit fixes its partner. Many XV puzzles also say that all Xs and Vs are given, which turns every blank border into a clue as well.

Worth memorizing

  1. X pairs

    1-9, 2-8, 3-7, 4-6. 5 can never touch an X.

  2. V pairs

    1-4 and 2-3. Only 1 to 4 fit on a V.

  3. When a puzzle says all Xs and Vs are given, two neighbors with no mark can’t add to 5 or 10.

    That rules out a lot.

Practice xv in the lesson

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