Stuck on a medium Sudoku? Stop guessing and find one fact
A harder grid may not have a nearly complete row. Do not choose the digit that looks most likely. Write the digits that can still fit in one empty cell. Each possible digit is called a candidate.
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One visible proof
When one cell has only one possible digit after you check its row, column, and 3×3 box, that digit is forced.
- 1. Choose one empty cellCheck its row, column, and 3×3 box.
- 2. Rule out the used digitsRow 1 contains 3, 5, and 6. Column 3 contains 2, 8, and 9. The top-left 3×3 box also contains 1 and 7. Together, these checks rule out every digit except 4.
- 3. Place the only candidateOnly candidate 4 remains, so 4 must go in the outlined cell. A cell with one candidate is called a naked single.
Row 1 rules out 3, 5, and 6. Column 3 rules out 2, 8, and 9. The top-left 3×3 box rules out 1 and 7. Only 4 remains.
Bring the exact Sudoku that stopped you.
Choose a screenshot or photo, or type the grid. The coach starts with where to look, explains the next logical move, and saves what tripped you up for short practice.
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