Medium

Hidden triple

What it is

Three digits that can only go in the same three cells of a unit – other candidates in those cells can be removed.

How to spot it

Count the places for each digit in a unit. If three digits are confined to the same three cells, those cells belong to them.

Example

Basis

In row 1, 1, 2 and 3 only appear in r1c2, r1c5 and r1c8. Those cells must hold 1, 2 and 3, so 4 and 5 are removed from r1c2, 6 from r1c5, and 4 and 6 from r1c8.

Used from level: Medium