Hidden Triple

Level: first needed in Master / Extreme puzzles. In one line: Three numbers restricted to the same three cells of a unit; other candidates in those cells go.

A Hidden Triple is three numbers that, within one row, column or box, can only be placed in the same three cells. Those three cells must hold those three numbers, so any other candidate in those cells can be removed.

As with naked triples, each number does not need to fit in all three cells; what matters is that together the three numbers are confined to exactly three cells.

Example from a real puzzle

This position comes from an Extreme puzzle in Sudoku Arena, at the exact moment the Hidden Triple is the next logical move. Cells are named by row and column: R3C4 means row 3, column 4.

Cells that form the patternCandidate you can remove

{3,4,7} can only go in R3C8, R8C8, R9C8 within column 8. Result: remove 2 from R8C8, 1 from R9C8.

Play this puzzle and look for the move yourself. It's a practice game, so it doesn't count towards your stats.

How to spot it

  1. In one unit, list where each missing number can go.
  2. Find three numbers whose possible places, combined, are only three cells.
  3. Remove all other candidates from those three cells.

Tips

  • Hidden triples are much easier to find with complete, accurate notes.
  • If a unit has many empty cells, check the "complement": the other cells may form a naked subset that is easier to see.

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