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Naked Pairs and Triples

The naked pairs technique is a very powerful candidate elimination technique, that is nevertheless quite easy to spot. Put simply, a naked pair occurs when two cells in a group can only contain two digits between them. If you spot this situation, it means that neither of the digits can occur anywhere else in that group. Here is an example:

In this example, the cells highlighted in yellow both contain either a "6" or a "7". Because they share a group, they cannot both have the same value, so if one of them is a "6" the other must be a "7" and vice-versa. The cell highlighted in red is in the same group, and therefore cannot be either a "6" or a "7", and both of these candidates can be eliminated from that cell.

It is also possible for naked triples to occur, although these are very rare. With a naked triple, there are three cells in a group which can only assume 3 values between them. Here is an example:

In this example, the cells highlighted in orange for a naked triple with the digits 3, 4 and 6. This allows us to eliminate the candidates "3", "4" and "6" from all the cells highlighted in red.

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