The New Sudoku Players' Forum

[Llama]

Superior Version 15

I'm pretty new to this - and have tried to solve this one 6 times!
If you don't have any doubles or trebles left, how do you eliminate the numbers?

[PaulIQ164]

Almost certainly, it's a tactic called "X-Wing" you've failed to discover. Poke around the forum, or google 'X-wing' with some terms like 'sudoku techniques' to filter out the Star Wars references and you should find an explanation.

[Crazy Girl]

Llama,

As you haven't stated how far you've got I'll start from the beginning. Applying basic principles you should get the following

Code: Select all

93--6817-
-7-4-----
------5-3
2--8-5-3-
-53----9-
-8-3-2-51
3-1------
-----7-1-
-47-2---5

So the candidates for each cell will be as follows

Code: Select all

+----------------------+----------------------+-----------------------+
|  9      3      245   |  25     6      8     |  1      7     24      |
|  1568   7      2568  |  4      135    139   |  2689   268   2689    |
|  1468   126    2468  |  1279   17     19    |  5      2468  3       |
+----------------------+----------------------+-----------------------+
|  2      169    469   |  8      1479   5     |  467    3     467     |
|  147    5      3     |  167    147    46    |  2478   9     2478    |
|  467    8      469   |  3      479    2     |  467    5      1      |
+----------------------+----------------------+-----------------------+
|  3      269    1     |  569    458    469   |  246789 2468  246789  |
|  568    269    25689 |  69     3458   7     |  234689 1     24689   |
|  68    4       7     |  169    2      1369  |  3689   68    5       |
+----------------------+----------------------+-----------------------+

*Naked {6, 8} pair in Row 9 so you can eliminate 6&8 from Row 9.
*Hidden {2, 8} pair in Block 6, Row 5 so 2&8 eliminated from Row 5, Also note Naked triple {4, 6, 7} in remaining cells in Box 6.
*The 9 in Block 3 has to appear in Row 2 so can eliminate 9 from the rest of Row 2 leaving a {1, 3, 9} triple in C6.
*Hidden {?, ?, ?} triple in Column 5, So now there is only one place for a 4 in Block 8.
*Then basic steps to complete puzzle.

If you are stuck on the terminology or need to update your skills, the following sites come highly recommended

http://www.angusj.com/sudoku/hints.php
or
http://www.simes.clara.co.uk/programs/sudokutechniques.htm

hope this helps

[Llama]

Thanks Crazy girl,
I got as far as the hidden triple (???) in column 5 - what does that mean as there are lots of different triples in that column - 147, 479, 458, 348. So how is it that the only place the 4 will go in block 9 is top right? Does it mean that if a 4 is in two different triples then it must go where there is a double?
Thanks for any help.

[SteveF]

Not sure I followed your last post Llama, but have a close look at column 5.

Crazy Girl is quite right that there is a hidden triple in the column, but as in all such cases there must also be a complementary naked grouping, in this case a naked quad. Personaly I find it easier to spot nakeds rather than hiddens.

So to find the naked quad, you need to find four cells that contain ONLY four candidates (each cell does not have to contain all four candidates).

To find the hidden triple is similar, you need to find three candidates are restricted to three cells. All other candidates in those three cells can be excluded.
Note that any (or all) of the three cells could have more than three candidates.

I think it is this last point that (for me) makes nakeds easier to spot.

[emm]

I think the hidden triple is a good find – it’s not easy to see. As Steve says - the quad in c5 is more obvious.

A hidden triple doesn’t mean any three numbers, it means 3 numbers that can only be found in the same three cells in a group. In this case = 3,5,8 => eliminate other candidates in those cells in column 5.

For comparison there’s a naked triple 4,6,7 in box 6 => eliminate 4,6,7 from all other cells in box 6.

Code: Select all

+----------------------+----------------------+-----------------------+
|  9      3      245   |  25     6      8     |  1      7     24      |
|  1568   7      2568  |  4     *135    139   |  2689   268   2689    |
|  1468   126    2468  |  1279   17     19    |  5      2468  3       |
+----------------------+----------------------+-----------------------+
|  2      169    469   |  8      1479   5     | *467    3    *467     |
|  147    5      3     |  167    147    46    |  2478   9     2478    |
|  467    8      469   |  3      479    2     | *467    5     1       |
+----------------------+----------------------+-----------------------+
|  3      269    1     |  569   *458    469   |  246789 2468  246789  |
|  568    269    25689 |  69    *3458   7     |  234689 1     24689   |
|  68    4       7     |  19     2      139   |  39     68    5       |
+----------------------+----------------------+-----------------------+

Code: Select all

+----------------------+----------------------+-----------------------+
|  9      3      245   |  25     6      8     |  1      7     24      |
|  1568   7      2568  |  4     *35     139   |  2689   268   2689    |
|  1468   126    2468  |  1279   17     19    |  5      2468  3       |
+----------------------+----------------------+-----------------------+
|  2      169    469   |  8      1479   5     | *467    3    *467     |
|  147    5      3     |  167    147    46    |  28     9     28      |
|  467    8      469   |  3      479    2     | *467    5     1       |
+----------------------+----------------------+-----------------------+
|  3      269    1     |  569   *58     469   |  246789 2468  246789  |
|  568    269    25689 |  69    *358    7     |  234689 1     24689   |
|  68    4       7     |  19     2      139   |  39     68    5       |
+----------------------+----------------------+-----------------------+

Then there’s another naked one in column 6.

[Llama]

Thanks a million to you all - Steve F, Crazy Girl and Em for helping me solve this puzzle.
All done - at long last.
Again, ta very much.