The New Sudoku Players' Forum

[5krunner]

I'm stuck at this point on this puzzle and was hoping someone could suggest a next step. Thanks in advance!! Jay.

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

[Animator]

The key to solving it is column 4.

Pencilmarks for the grid: (note: these are the initial pencilmarks. Some canidates can be removed. (for example the 2 and the 3 in r1c2 and r3c2.)

Code: Select all

5  2349  23 | 6      23478  2379 | 237  2378  1
1  6     7  | 5      238    23   | 9    238   4
8  2349  23 | 23479  1      2379 | 237  5     6
------------+--------------------+-------------
4  1     6  | 237    2357   2357 | 8    37    9
3  78    5  | 4789   4678   679  | 1    67    2
2  78    9  | 1378   3678   1367 | 367  4     5
------------+--------------------+-------------
6  25    8  | 127    9      1257 | 4    12    3
9  23    4  | 123    236    8    | 5    126   7
7  235   1  | 23     2356   4    | 26   9     8


If you look carefully at column 4 then you see a hidden triple and a naked quad.

The triple: 489: there are exactly three cells that can have one of those 3 numbers. (r3c4, r5c4, r6c4)
Naked quad: 1237: there are exactly 4 cells that share the same 4 candidates. (r4c4, r7c4, r8c4, r9c4)

This allows you to remove the following candidates:

• 237 from r3c4 leaving 49
• 7 from r5c4 leaving 489
• 137 from r6c4 leaving 8

Leaving you with this grid:

Code: Select all

5  2349  23 | 6      23478  2379 | 237  2378  1
1  6     7  | 5      238    23   | 9    238   4
8  2349  23 | 49     1      2379 | 237  5     6
------------+--------------------+-------------
4  1     6  | 237    2357   2357 | 8    37    9
3  78    5  | 489    4678   679  | 1    67    2
2  78    9  | 8      3678   1367 | 367  4     5
------------+--------------------+-------------
6  25    8  | 127    9      1257 | 4    12    3
9  23    4  | 123    236    8    | 5    126   7
7  235   1  | 23     2356   4    | 26   9     8


[5krunner]

Animator,

That's amazing ... I see the the triple and quad now you mentioned ... would have had a hard time seeing that on my own. I have a way to go to master these harder puzzles. Thank you!!!

Jay.

[gsf]

The key to solving it is column 4.

col 4 has a hidden double {49}

[5krunner]

I see that too now!! Thanks!! I need to be able to spot these myself.

[MCC]

If you look at the 6's in box 8, you'll find that they are locked in column 5, so you can remove the 6's in box 5, r5c5 and r6c5.


MCC