Medium Killer Sudoku — Sums Start to Matter

Medium Killer Sudoku is rated 2.0 to 2.9, still basic tier, with fewer starting digits than easy. This is where the cage sums turn from hints into real constraints. It suits players who can finish a classic medium and want a puzzle that adds up.

What this level asks

Plain singles run out sooner than in a classic medium, and the sums supply the next step. Two things do most of the work: the 45 rule (every row, column and box totals 45) and the short list of digits a cage can hold. Four-cell cages leave more room than small ones, so compare them with their neighbours. A good routine for a fresh board: total up each row, column and box, note which cages sit wholly inside them, and see what is left over. That leftover often names a single cell, and one placed digit then unlocks the cages around it.

29

Possible combinations: 1

• 5789

Techniques you will meet

• Cage combinations on almost every sum. The cage above must be 5, 7, 8 and 9.
• Innies and outies: a single odd cell found by subtracting cage sums from 45 (project rating 2.0).
• Captured candidates (2.7): a digit confined to one cage cannot sit elsewhere in the unit they share.
• Cage and unit overlap (2.7) in the harder mediums.

Tips for this level

• Do the 45 rule on every box and band before you hunt for anything else.
• Strike a digit from a cage note as soon as its row, column or box rules it out.
• Stuck? Find the cage with the fewest allowed combinations and start there.

Next step

Finishing medium grids without hints? Try hard Killer. Want more practice with the basics first? Easy Killer is one level down.