Hidden Pair
Hard
Used by Smart Hint
Two digits guaranteed to appear in this run only fit in the same two cells — strip those cells down to just those two.
- Cells that establish the pattern
- Where the conclusion lands
- Digit ruled out
How it works
- Four 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.
- But the first two cells have already lost 8 and 9 to their crossing runs. Only the last two can hold them.
- Two guaranteed digits with only two cells to live in: those cells are the 8 and the 9, in some order.
- Strike everything else from both — even though neither is pinned to a single digit yet.