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Naked Single

Naked SingleSTEP 1/3

Introduction to the Strategy

It's time for the Naked Single strategy. We use it when we look at one specific cell and check which digits can possibly go there:

Analyze the row, column, and box intersecting that cell
List all digits that are already blocked

If only one option remains after removing the blocked digits, you can safely enter it into the cell.

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Naked SingleSTEP 2/3

Scanning the Constraints

Look at the cell the game has just highlighted on the board. See how many digits restrict it from different directions:

Several digits already appear in its row and column
There are also additional numbers in its 3×3 box

All these visible digits "intersect" on this single cell and eliminate themselves.

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Naked SingleSTEP 3/3

Elimination and Entry

Keep all the digits visible in the highlighted row, column, and box in mind.

Discard the digits from 1 do 9 that already appear there
Notice that only one possibility remains for this cell. The digit is 1

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