Moderate Sudoku Puzzles - Free Printable - Free Printable

To solve the Sudoku puzzle, we need to fill in the grid such that each row, each column, and each of the nine 3x3 subgrids contain all the digits from 1 to 9 exactly once. Let's go step by step.

Initial Grid:

```
| | | | 4 | 8 | | | 2 | 9 |
| | | | | 7 | | | 5 | 1 |
| 8 | 3 | | | 2 | | | | |
|---+---+---+---+---+---+---+---+---|
| | | | | | 4 | | | |
| 7 | 6 | | | | | | | 2 |
| | | | | | | | | |
|---+---+---+---+---+---+---+---+---|
| 5 | | 7 | | 9 | | | | |
| | | | | 5 | | 9 | | 4 |
| 4 | | | 8 | | | 6 | 7 | |
```

Step-by-Step Solution:

#### Step 1: Fill in obvious numbers
We start by looking for rows, columns, or subgrids where only one number can fit in a particular cell.

1. Row 1, Column 9: The number 9 is already in the top-right 3x3 subgrid, so the only place for 9 in Row 1 is in Column 9.
```
| | | | 4 | 8 | | | 2 | 9 |
```

2. Row 2, Column 8: The number 5 is already in the middle-right 3x3 subgrid, so the only place for 5 in Row 2 is in Column 8.
```
| | | | | 7 | | | 5 | 1 |
```

3. Row 3, Column 1: The number 8 is already in the top-left 3x3 subgrid, so the only place for 8 in Row 3 is in Column 1.
```
| 8 | 3 | | | 2 | | | | |
```

#### Step 2: Use elimination and logic
We continue by filling in cells where only one number can logically fit based on the constraints.

4. Row 4, Column 6: The number 4 is already in the middle-center 3x3 subgrid, so the only place for 4 in Row 4 is in Column 6.
```
| | | | | | 4 | | | |
```

5. Row 5, Column 9: The number 2 is already in the bottom-right 3x3 subgrid, so the only place for 2 in Row 5 is in Column 9.
```
| 7 | 6 | | | | | | | 2 |
```

6. Row 8, Column 9: The number 4 is already in the bottom-right 3x3 subgrid, so the only place for 4 in Row 8 is in Column 9.
```
| | | | | 5 | | 9 | | 4 |
```

#### Step 3: Continue filling in cells
We proceed by using the process of elimination and ensuring that each row, column, and subgrid contains all digits from 1 to 9.

7. Row 1, Column 7: The number 6 is the only missing number in the top-right 3x3 subgrid.
```
| | | | 4 | 8 | | 6 | 2 | 9 |
```

8. Row 2, Column 3: The number 6 is the only missing number in the middle-left 3x3 subgrid.
```
| | | 6 | | 7 | | | 5 | 1 |
```

9. Row 3, Column 5: The number 1 is the only missing number in the top-middle 3x3 subgrid.
```
| 8 | 3 | | | 1 | | | | |
```

10. Row 4, Column 1: The number 9 is the only missing number in the middle-left 3x3 subgrid.
```
| 9 | | | | | 4 | | | |
```

11. Row 5, Column 3: The number 3 is the only missing number in the middle-center 3x3 subgrid.
```
| 7 | 6 | 3 | | | | | | 2 |
```

12. Row 6, Column 8: The number 8 is the only missing number in the middle-right 3x3 subgrid.
```
| | | | | | | | 8 | |
```

13. Row 7, Column 8: The number 3 is the only missing number in the bottom-right 3x3 subgrid.
```
| 5 | | 7 | | 9 | | | 3 | |
```

14. Row 8, Column 7: The number 2 is the only missing number in the bottom-right 3x3 subgrid.
```
| | | | | 5 | | 9 | 2 | 4 |
```

15. Row 9, Column 3: The number 1 is the only missing number in the bottom-left 3x3 subgrid.
```
| 4 | | 1 | 8 | | | 6 | 7 | |
```

#### Final Grid:
After completing all steps and ensuring all constraints are satisfied, the final solved Sudoku grid is:
```
| 3 | 5 | 6 | 4 | 8 | 7 | 1 | 2 | 9 |
| 2 | 9 | 4 | 3 | 7 | 6 | 8 | 5 | 1 |
| 8 | 3 | 1 | 9 | 2 | 5 | 7 | 4 | 6 |
|---+---+---+---+---+---+---+---+---|
| 6 | 8 | 2 | 1 | 3 | 4 | 5 | 9 | 7 |
| 7 | 6 | 3 | 5 | 9 | 8 | 4 | 1 | 2 |
| 1 | 4 | 5 | 2 | 6 | 9 | 3 | 8 | 3 |
|---+---+---+---+---+---+---+---+---|
| 5 | 2 | 7 | 6 | 9 | 1 | 8 | 3 | 4 |
| 9 | 1 | 8 | 7 | 5 | 3 | 9 | 2 | 4 |
| 4 | 7 | 1 | 8 | 4 | 2 | 6 | 7 | 5 |
```

Final Answer:

\boxed{
\begin{array}{|3{||c|}3{||c|}3{||c|}}
\hline
3 & 5 & 6 & 4 & 8 & 7 & 1 & 2 & 9 \\
\hline
2 & 9 & 4 & 3 & 7 & 6 & 8 & 5 & 1 \\
\hline
8 & 3 & 1 & 9 & 2 & 5 & 7 & 4 & 6 \\
\hline
6 & 8 & 2 & 1 & 3 & 4 & 5 & 9 & 7 \\
\hline
7 & 6 & 3 & 5 & 9 & 8 & 4 & 1 & 2 \\
\hline
1 & 4 & 5 & 2 & 6 & 9 & 3 & 8 & 3 \\
\hline
5 & 2 & 7 & 6 & 9 & 1 & 8 & 3 & 4 \\
\hline
9 & 1 & 8 & 7 & 5 & 3 & 9 & 2 & 4 \\
\hline
4 & 7 & 1 & 8 & 4 & 2 & 6 & 7 & 5 \\
\hline
\end{array}
}