Solved Exercise on How To Solve Sudoku Puzzles: 3

8

1

7

2

9

7

2 1

3

8

1

Cells (1,5), (6,9) and (7,8) take the values '5', '5' and '4' respectively by the same method.

Now, Cells (1,4), and (5,9), take the values '6', and '8' respectively (by the Hidden Singles Approach for How To Solve Sudoku Puzzles).

Consequently, Cell (8,7) takes the value '9' by Naked Singles Approach for How To Solve Sudoku Puzzles Similarly, Cells (8,8) and (9,8) take the values '7' and '6' respectively.

In Top Middle Major Square we need '4'. Cells ( 3,5) or (3,6) can take the value '4'. Other unfilled Cells in Top Mid Major Square can't take value '4' since they already have a '4' in their respective Columns. Let's now try to identify all the possible values in R3, and then see if we  could eliminate some of these possibilities or fix the value '4'.

By Direct Interaction Approach for How To Solve Sudoku Puzzles, we can eliminate possibility of '4' in  the other Cells of R3. That is, we get '9' in the Cell (3,9).

After assigning this value, we get the value '4' in the Cell (1,9) by Naked  Singles Approach for How To Solve Sudoku Puzzles. Now, by Reduction Approach for How To Solve Sudoku Puzzles, we get the values of Cells (1,7) & Cells (1,2) as '3' & '9' respectively.

In Column 2, Cells ( 2, 2 ) & ( 3, 2 ) have the same unique set of  possible values, '1' & '3'. This means, the values '1' and '3' cannot be taken by any other Cell in C2. In such a case, Naked Subsets Approach for How To Solve Sudoku Puzzles allows us to eliminate the values '1' & '3' in the other possible Cells of

C2. So, we get the value of Cell (7,2) as '5'.

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