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| We can easily extend Hidden Pairs to Hidden Triples or even Hidden Quads. A Triple will consist of three pairs of numbers lying in three cells in the same unit (row, column or box), Such as 4/8/9, 4/8/9 and 4/8/9 hidden behind other candidates However, Hidden Triples are more interesting and follow a similar idea as Naked Triples. We don't need exactly three pairs of numbers in three cells for the rules to apply. In the example below we have 1/4/6, 1/4 and 1/4/6 in three cells. |
Fig. 8.1 |
Just like Naked pairs we can extend Hidden Pairs and Triples to Quads and even beyond.
These are extremely hard to spot! |
Fig. 9.1 |
In column 8 we have a Hidden Quad with the numbers 3/5/6/7 spread over B8, D8, E8 and F8. The Quad is barely hidden – just by one number. But logic ensures that the 4 in B8 can be safely removed, and ensure that Sudoku can be solved. |
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