Naked Triples
As the name suggests, this method is very similar, and works in the same way as Naked Triples, but
with three cells. The only difference is that not every cell should contain all 3
candidates. We would only like to have 3 cells which contain 3 different candidates in total.
Naked Triples - Example 1
To make this more clear let us consider the following example. A Naked Triple appears in row H with cells H7, H8 and H9. We see that the candidates {2, 3, 4} will be the exact values in these three cells, but we do not know in which order. What we can be sure of, is that {2, 3, 4} are not possible values for any other empty cell in row H. Hence we can eliminate all candidates in red.
Notice that in the above example, cell H9 only contains 2 and 3, out of
the triple {2, 3, 4}. This should not be a concern. We only use the argument that there are
3 different candidates in total among three cells.
To convince ourselves why this method
works, consider placing a 4 in cell H2. This will eliminate the candidate 4
from H7 and H8. We will be left with 3 cells with exactly 2 candidates between them
which is not possible.
In the same board after a couple of steps, we come across a 2-2-2 combination in the same row. The three cells H1, H2 and H3 contain among them a total of three candidates {1, 6, 9}. Therefore, we can eliminate all candidates with these values in row H (given in red).
Naked Triples - Example 2
Again, as with all other basic methods, a Naked Triple can appear also in a column or a square. Here is an example of a Naked Triple in column 4. The dark blue cells D4, F4 and I4 form a 2-2-3 combination with candidates {1, 2, 7}. Hence we can eliminate the candidates in red in the same column.
