Killer Sudoku rules and puzzles

The case notes

Use a modular line to choose a Killer cage pair

This fifteen-cage sits on the start of a modular line. Each rule gives us part of the story; together they settle the cage’s two digits. Watch a worked example, then try the idea in a puzzle.

Put it into practice

A 15-cage on a modular line

This fifteen-cage sits on the start of a modular line. Each rule gives us part of the story; together they settle the cage’s two digits.

15 = 6 + 9 = 7 + 8

Two different Sudoku digits add to fifteen in just two ways: six and nine, or seven and eight. The cage alone cannot choose between them.

6 and 9 share a group

A modular line needs one digit from each of its three groups across these three cells. Six and nine are in the same group. They cannot occupy the first two positions together.

The cage is {7, 8}

That leaves seven and eight. They belong to different modular groups, so the line accepts them. We know the pair, though not yet its order.

Read the transcript

This fifteen-cage sits on the start of a modular line. Each rule gives us part of the story; together they settle the cage’s two digits. Two different Sudoku digits add to fifteen in just two ways: six and nine, or seven and eight. The cage alone cannot choose between them. A modular line needs one digit from each of its three groups across these three cells. Six and nine are in the same group. They cannot occupy the first two positions together. That leaves seven and eight. They belong to different modular groups, so the line accepts them. We know the pair, though not yet its order.

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