The New Sudoku Players' Forum

[geocant]

In a solving unit (row, column, or large box), with 4 remaining empty squares, is it just a guess to try and create 2 mutually exclusive number pairs?

For example, remaining possibilities in the unit are 248, 248, 249, and 49.
Taking a clue from the single pair, is it valid to delete the 4's from the two 248 triplets, and the 2 from the 249 triplet, thus ending up with the possibilities: 28, 28, 49, 49 ? Is this mathematically valid or just a guess?

Any thoughts would be appreciated.

geocant

[vidarino]

I'm afraid there isn't a logical reason these should form pairs under just these circumstances. For the numbers you listed (248, 248, 249 and 49) there are several solutions;

Code: Select all

2 8 4 9
2 8 9 4
4 8 2 9
8 4 2 9
8 2 4 9
8 2 9 4

(... any maybe more, I didn't check too thoroughly)

So if you try to treat them as pairs, there is a good chance you'd end up making a wrong elimination.