IntermediatePractice
Practise: Rule of 45
This Killer puzzle stalls at exactly the point where Rule of 45 is needed. Work it out yourself, or jump straight to that position.
Skip the obvious cells and start where the technique matters.
Practice
Mistakes0Score2,000Time0:00
How to spot it
Pick a row, column or box where cages mostly stay inside. Add the sums of the cages fully contained in it, then compare with 45. The difference is the total of the remaining cells.
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Put it to use
Where you will meet it
Hard grids are built around moves like this one. That is where it earns its keep.
Play HardStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
Open the solver