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.
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
Common names for values of N:
- N = 2: Naked Pair
- N = 3: Naked Triplet
- N = 4: Naked Quad
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