Variant Sudoku

Region Sum Lines Explained in One Short Example

0:15 · Region sum lines · Variant Sudoku

A five-cell line crosses a box border. The piece in the first box is 1, 2 and 6, which adds up to 9, so the piece in the next box must also make 9 with 4 and 5.

Full lesson and practiceFind Region Sum Lines puzzles

Transcript

  1. 0:02Where a line crosses box borders, each piece of it sums to the same total.
  2. 0:06The piece in the first box adds to 9...
  3. 0:09...so the piece in the next box must too: 4 + 5 = 9.

The rule

A region sum line is usually blue. Where it crosses from one 3x3 box into another, the border cuts it into pieces, and every piece has the same sum.

The rule links distant parts of the grid. A short piece limits how big a long piece can be, and a long piece forces the short one to be large.

Worth memorizing

  1. A single-cell segment sets the total for every other segment.

  2. Segments with more cells need smaller digits to match shorter ones.

Practice region sum lines in the lesson

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