The case notes
Use the rule of 45 to find an arrow circle
Here, two Killer cages and an arrow meet in one Sudoku row. The cages cover seven cells; the arrow shaft takes the other two. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Cages beside an arrow
Here, two Killer cages and an arrow meet in one Sudoku row. The cages cover seven cells; the arrow shaft takes the other two.
45 − 18 − 24 = 3
The whole row totals forty-five. The cages give eighteen and twenty-four, making forty-two. That leaves three for the two shaft cells together.
Circle = shaft total
An arrow circle equals its shaft’s sum. We do not need to know which shaft cell is one or two yet. Their total already fixes the circle.
The circle is 3
The circle is three. The rule of forty-five gave us the missing sum, and the arrow carried that sum to a different cell.
Read the transcript
Here, two Killer cages and an arrow meet in one Sudoku row. The cages cover seven cells; the arrow shaft takes the other two. The whole row totals forty-five. The cages give eighteen and twenty-four, making forty-two. That leaves three for the two shaft cells together. An arrow circle equals its shaft’s sum. We do not need to know which shaft cell is one or two yet. Their total already fixes the circle. The circle is three. The rule of forty-five gave us the missing sum, and the arrow carried that sum to a different cell.
Keep following the clues
- Killer Sudoku rules: cage sums and no repeated digits →
- Killer Sudoku cage combinations: find the digits in a small cage →
- Killer Sudoku rule of 45: find a missing digit in a row →
- Killer Sudoku: Find an outie from a Killer box →
- Arrow Sudoku: How an arrow adds up →
- Killer Sudoku: add cage sums to find a shared digit set →
- Killer Sudoku: Use a box to constrain a crossing Killer cage →
- Killer Sudoku: Compare two Killer cages through their shared row →
- Killer Sudoku: Let a Killer cage rule out digits nearby →
- Killer Sudoku: Use a sum you worked out as an invisible cage →
- Killer Sudoku: Use a modular line to choose a Killer cage pair →
- Killer Sudoku: Find two missing cells with the rule of 45 →
- Arrow Sudoku: Subtract an overlapping cage from an arrow →
- Arrow Sudoku: Reject an arrow bulb that empties its box →