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Elimination

EliminationSTEP 1/3

Introduction

Time for a fundamental technique: Process of Elimination. As the board gets more crowded, the key is not to look for the correct digit, but to:

Gradually eliminate digits that definitely cannot go there
Use notes to keep track of the remaining options

By eliminating impossible scenarios, whatever remains - even if it seems unlikely - must be true.

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EliminationSTEP 2/3

Analyzing Notes

Look at the highlighted cell and the candidates written inside it. The game has also highlighted the related row, column, and 3×3 box:

Notice which digits are already present in the lines intersecting this cell
Compare them with the list of candidates in our cell

Each digit in this "cross" automatically eliminates its corresponding candidate from our cell.

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EliminationSTEP 3/3

Cleaning Up the Notes

We will apply the elimination process. We remove from the notes any candidates that cannot go in this cell:

Eliminate candidates that conflict with the row, column, or box
Notice that after crossing out the impossible options, only one digit remains.

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