Techniques · Hard
Hidden triple
A hidden triple is three digits that, inside one house, fit in only three cells. The cells may have other candidates written on them. Those extras are wrong: the three digits have to occupy the three cells, so anything else on them is eliminated.
It is the hidden-pair idea with one more digit. Once the extras are gone, the three cells read as a naked triple.
When it shows up
Hidden triples are Hard, alongside naked triples and both kinds of pair.
Triples of either kind are the hardest step on 6% of NYT Hard. No archived NYT puzzle needs a quad, a fish, or a chain.
See it on a real puzzle
The marks are the candidates left when this is the next step in the solve. Step through it: the pattern, what leaves, and what that forces.
See the pattern
Look at these three cells.
3
2
4
8
6
1
7
1
9
7
6
2
5
3
2
7
6
1
4
8
9
3
7
8
5
5
1
6
9
3
4
1
9
6
2
4
5
7
9
3
6
4