Kakuro Revisited

Hidden Pairs and Triples in a Run

Two digits that can only go in the same two cells of a run are locked there, so those cells lose every other candidate.

Level 3 Subsets in a run Technique 09

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In Down 19 (r4c8–r7c8), the digits 1 and 2 can only go in r4c8 and r5c8. Those cells must be 1 and 2, so 5, 9, 6 and 8 are removed from them.

key digits removed

Why it works

The mirror image of a naked pair. If the digits 1 and 2 fit only the cells r4c8 and r5c8 of a run, then those two cells must hold 1 and 2 in some order, whatever else they look like they could hold.

That means every other candidate in those two cells is impossible, and it can be removed.

How to spot it

  1. For each empty cell of a run, list its candidates.
  2. Find a digit that appears in only one cell, or two digits that appear in only the same two cells.
  3. The cells of a hidden pair hold those digits, so remove their other candidates.

Practice it

Open the app, choose a level that uses this technique, and ask the coach for the next step. Every hint links back to this guide.