Naked Subset
If there are N cells in one unit that contain N candidates between them, then the candidates can be removed from all the other cells in the unit.
Consider the sudoku below.
In the center block, the cells r4c6 and r5c6 have exactly two candidates, 6 and 7, between them. So we can remove the candidates 6 and 7 from all other cells in the center block. Notice that we could also apply this rule to column 6.
Common names for values of N:
- N = 2: Naked Pair
- N = 3: Naked Triplet
- N = 4: Naked Quad
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