GridWits
Hard tier Technique 8 of 20 Used by Smart Hint

Hidden Pair

Two digits guaranteed to appear in this run only fit in the same two cells — strip those cells down to just those two.

How it works

  1. 1Four cells summing to 28 can only be {4, 7, 8, 9} or {5, 6, 8, 9} — both ways, an 8 and a 9 appear somewhere in the run.
  2. 2But the first two cells have already lost 8 and 9 to their crossing runs. Only the last two can hold them.
  3. 3Two guaranteed digits with only two cells to live in: those cells are the 8 and the 9, in some order.
  4. 4Strike everything else from both — even though neither is pinned to a single digit yet.
28 4 5 6 7 4 5 6 7 5 6 8 9 4 7 8 9
  • Cells that establish the pattern
  • Where the conclusion lands
  • Digit ruled out
Next in the ladder Arrangement Check →

A combination has to fit the cells, not just the total: if every combination containing this digit leaves some other cell in the run with nothing it can take, the digit is impossible here. Two or three combinations to weigh.