Naked Triplet is not as common as Naked Pair since it is a bit more complicated. Unlike Naked Pair, Naked Triplet does not imply all three numbers in three cells. Any group of three cells in the same unit that contain in total three candidates (while each cell must contain at lease two candidates) is a Naked Triplet. That is, all three cells have three numbers all together. If this happens, the three candidates can be removed from all other cells in the same unit. For example, for number set {2, 4, 5}, any three-cell-group in a unit which contains any of the following combinations of candidates is a Naked Triplet:
{2, 4, 5} {2, 4, 5} {2, 4, 5}, or
{2, 4} {4, 5} {2, 5}, or
{2, 4, 5} {2, 5} {4, 5}, or
{2, 4, 5} {4, 5} {2, 4, 5}, or
...
However, cells that contain the following combinations cannot be called Naked Triplet:
{2, 4, 5} {2, 4} {2, 4}
Since {2, 4} and {2, 4} form a Naked Pair, so that only number 5 will be left in the number set {2, 4, 5} and Naked Single Technique can be applied.
Here is an example to apply Naked Triplet Technique:
In Row D, cells [D1], [D7] and [D8] contain numbers {3, 5, 9}, {3, 5, 9} and {5, 9} respectively, which is a combination of number set {3, 5, 9}. Then we can remove 3, 5 and 9 from the other cells in this row.
Below is another example:
In Column 2, cells [G2], [H2] and [I2] form a Naked Triplet of numbers {2, 5, 6}, so we can remove these three values from [A2], [B2] and [E2] in the same column.
Of course, we can also find Naked Triplet in blocks:
In Block at [D7], we can find a Naked Triplet cell-set of [D8], [D9] and [E9] for numbers 4, 8 and 9. In this case, the cells which can be updated are [E7] and [E8] in the same block.
See Also:
