Sum elimination tactics shrink Killer Sudoku candidate sets by comparing cage clues with Sudoku's mandatory 45-per-line arithmetic. Instead of hunting fish immediately, solvers exploit budgets—what cage totals remain permissible given digits already placed—to erase pencil marks aggressively.
Residual row arithmetic
Subtract placed digits and committed cage sums from 45 to expose leftover budgets for ambiguous cages.
Cage budget clashes
When two cages compete for narrow intersections, compare permissible tuples—often one tuple overspends row budgets.
Parity elimination
Odd-even mismatch between remaining cage totals and candidate residues kills tuples instantly.
Pairing with classic scans
Alternate sum elimination passes with Sudoku singles sweeps—each feeds the other.
Further study
Connect to cage combinations and advanced solving methods.