Intermediate technique · 05
Three cells collectively reserve three candidates.
The idea
A Naked Triple occurs when three cells in one house collectively contain only three same candidates, allowing to remove those three candidates from all other cells in the house. The individual cells do not need to contain all three numbers.
The question: Do these three cells contain only three candidates between them?
Walkthroughs
Each of those three cells does not have to be exact three condidates, but must be exact three numbers combined.
Walkthrough
Digits 2, 5 and 7 forms a Naked Triple in row 2 because those three numbers are only presented in cells r2c1, r2c3 and r2c9, no other cells in row 2 can contain those three numbers and no other numbers can be those three cells' candidates.
What to notice: Only look at houses with six or more unsolved cells, most likely you could find a naked triple in those houses.
Walkthrough
In this example, numbers 3, 6 and 9 forms a Naked Triple in row 4 because those three numbers are only presented in cells r4c2, r4c3 and r4c9, so those three numbers can be removed from the rest of cells in row4.
What to notice: You may notice that there actually is a Hidden Triple with numbers 2, 7 and 8 in cells r4c1, r4c7 and r4c8, which results the same number deduction. This tells that certain techniques are "exchangeable", meaning using one or another will give thesame candidate decution, but knowing all will certainly make solving puzzle faster and enjoyable.
How it works
In a house, those three numbers must occupy those three cells in some order, so none can appear elsewhere in the house.
Look at a row, column or box that has six or more unsolved cells.
Find three cells whose combined candidate set contains exactly three numbers.
Remove the three subset numbers from the other cells of the same house.
A useful reminder
Naked Subset, Naked Triple are related terms you may encounter while learning this technique. The important part is understanding the constraint and why the elimination follows from it.
Watch & learn
Comming soon...
Practice
Once you can explain why the pattern is valid, practice finding it in a few real puzzle positions before moving on.
