How it works
Hidden triples mirror naked triples the way hidden pairs mirror naked pairs. The trick is to scan digit positions, not cell contents.
If three digits can each only go in three specific cells of a unit, those digits must occupy those three cells. The remaining candidates inside those cells can be stripped away.
Hidden triples are rare, which is why they earn their name. When you do spot one, the cleanup usually produces multiple immediate placements.
When to look for it
When hidden pairs run out and candidate sets are still dense. Hidden triples are uncommon but high-payoff.
Tips for spotting the pattern
- Pick three digits with sparse position counts in a unit. Their possible locations may overlap precisely.
- Hidden triples in boxes show up most often. Scan boxes one digit at a time.
- If two digits form a hidden pair, check whether a third digit joins them. Hidden pairs often hint at hidden triples.
Common mistakes
- Looking at cell candidates instead of digit positions. The scan has to be digit-first.
- Allowing a fourth digit to share the three cells. That breaks the triple definition.
- Not stripping the extra candidates from the three cells once spotted.