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Having trouble with this...

Postby skibum » Tue Feb 14, 2006 2:05 am

This is a puzzle from a pappocom computer program and is rated very hard. The program tells me when I've made an incorrect entry of a big number. I've started over once and am stil stuck. Thank you.

[/code]146-7-14-5-9-8-23-46-23
48-9-5-237-2367-367-17-48-16
3-68-2-1-4-67-78-9-5
7-4-6-239-123-139-23-5-8
1289-128-1389-4-12378-5-6-17-23
5-128-138-2378-123678-1367-9-17-4
14689-3-1489-89-18-2-5-468-7
1489-1568-14789-3789-13578-1379-148-2-169
1289-1258-1789-6-1578-4-18-3-19
Code: Select all
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Postby TKiel » Tue Feb 14, 2006 4:18 am

Skibum,

Look at the candidate 1's in row 4. This allows some eliminations in box 5. That should reveal a naked triple (or hidden pair) in column 6. A naked triple (or hidden triple) in box 8. Then some locked candidates in box 8. Then singles.

Tracy
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Postby tarek » Tue Feb 14, 2006 5:19 am

hi skibum,

according to your pencilmarks, you should first look at column 7, The candidate 4 appears in only one cell in that column.

according to rules of sudoku, that cell must be 4. This is called a hidden single.


Tarek
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Postby QBasicMac » Tue Feb 14, 2006 5:32 am

You get to here via nothing more complicated than a hidden pair:
Code: Select all
+--------------------+------------------+----------------+
| 146    7     14    | 5     9      8   | 23    46   23  |
| 468    9     5     | 237   2367   367 | 1478  468  16  |
| 3      68    2     | 1     4      67  | 78    9    5   |
+--------------------+------------------+----------------+
| 7      4     6     | 239   123    19  | 23    5    8   |
| 1289   128   1389  | 4     2378   5   | 6     17   23  |
| 5      128   138   | 2378  23678  367 | 9     17   4   |
+--------------------+------------------+----------------+
| 14689  3     1489  | 89    18     2   | 5     468  7   |
| 14689  1568  14789 | 3789  13578  19  | 148   2    169 |
| 1289   1258  1789  | 6     1578   4   | 18    3    19  |
+--------------------+------------------+----------------+


At which point the naked triple 89-18-19 in box 8 eliminates all other 189 in box 8.

After that, it is pretty much a cake walk.

Mac
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Postby skibum » Wed Feb 15, 2006 6:03 am

Thank you all very much! I think I stared at this one too long without really concentrating. I appreciate your help. Thanks again, donetta
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