GridWits

Hidden Quad

Expert Used by Smart Hint

Four guaranteed digits only fit in the same four cells of a run — strip those cells down to just those four.

37 2 3 4 5 2 3 4 5 2 6 7 8 3 6 7 9 4 7 8 9 5 6 8 9

How it works

  1. Six cells summing to 37 means three digits are missing from 1-9 and they add to 8 — only {1, 2, 5} or {1, 3, 4}.
  2. So the run is either {3, 4, 6, 7, 8, 9} or {2, 5, 6, 7, 8, 9}: a 6, a 7, an 8 and a 9 are guaranteed either way.
  3. None of those four fit in the first two cells, so they must fill the last four — one apiece.
  4. Strike the leftover small candidate from each of those four cells.