obvious triples
level 4 - hardalso known as: naked triples
what it means
three cells contain only three different numbers between them. those three cells own those three numbers, so you can remove them from other cells.
two types of obvious triples
type 1: pure triple
each cell has exactly 2 candidates. together they form 3 unique numbers.
[1, 2]
[1, 3]
[2, 3]
type 2: with subset
one cell has all 3 candidates, others are subsets.
[1, 2, 3]
[1, 2]
[1, 3]
example 1: pure triple
three cells with [2,5], [2,8], [5,8] — together only numbers 2, 5, 8.
highlighted cells form the triple
example 2: triple with subset
one cell has all three: [3, 6, 9], [3, 6], [3, 9]
example 3: before and after elimination
the triple owns 3, 6, and 9. we eliminate those from other cells.
before
after
key concept: they own those numbers
think of it like three friends ordering lunch. between them, those three items must be distributed — and nobody else can have them!
the chain reaction
eliminating candidates often creates new obvious singles!
before
after
summary
- find three cells that together contain only three unique candidates
- pure triple: each cell has exactly 2 candidates
- with subset: one cell has all 3, others are subsets
- those three numbers must occupy those three cells
- remove those candidates from all other cells in the unit
- watch for new singles revealed by elimination!