times book 1 puzzle 80

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times book 1 puzzle 80

Postby darren » Sun Mar 19, 2006 5:56 pm

516439782
xx4712569
x7x568413
x2xx9417x
xxxx81x3x
x61x57x48
xxx9x6851
6xx12539x
1xx8x362x

This is how far I have got with this one. Can anyone help with the next move.
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Postby tarek » Sun Mar 19, 2006 7:51 pm

Hi there,

couldn't tell how far you progressed in this puzzle.

Assuming a steady progression though, you should hit this question.....


Look at column 1 & look at candidates 3 & 8 possible placements, any conclusions ?

Tarek
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Postby darren » Tue Mar 21, 2006 11:01 pm

Tarek,

Thanks for this reply, but think I have looked at this one too long. With your help I still can't see a way forward. Looking at column 1, position 2 can either be a 3 or 8. But so can position 4. Position 6 could be a 3 and position 7 could be a 3. Any other hints.

Darren.
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Postby CathyW » Tue Mar 21, 2006 11:25 pm

Code: Select all
 
 *-----------------------------------------------------------*
 | 5     1     6     | 4     3     9     | 7     8     2     |
 | 38    38    4     | 7     1     2     | 5     6     9     |
 | 29    7     29    | 5     6     8     | 4     1     3     |
 |-------------------+-------------------+-------------------|
 | 38    2     358   | 36    9     4     | 1     7     56    |
 | 479   459   579   | 26    8     1     | 29    3     56    |
 | 39    6     1     | 23    5     7     | 29    4     8     |
 |-------------------+-------------------+-------------------|
 | 2347  34    237   | 9     47    6     | 8     5     1     |
 | 6     48    78    | 1     2     5     | 3     9     47    |
 | 1     459   579   | 8     47    3     | 6     2     47    |
 *-----------------------------------------------------------*

Perhaps it's a bit clearer with a candidate list.:)
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Postby darren » Wed Mar 22, 2006 12:50 am

I found the following message elsewhere on the site."A pair of cells is where you can find 2 cells in a box, row or column that can only have
2 possible numbers in them. Pairs are extremely useful as they mean you can rule out those
same 2 numbers being anywhere else in that box, row, or column in question. "


Using this information and the candidate list I believe that the next number that can go in is 9 in column 1 position 6 as the 3 and 8 are ruled out anywhere else in this column.
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Postby TKiel » Wed Mar 22, 2006 2:31 am

Darren,

Two cells which contain only the same two values are a 'naked pair'. Those two values can be excluded from all other cells in the same group. Two values that are found in only the same two cells are a 'hidden pair'. All other values in those two cells can be excluded. You'll find plenty of use for these in your Sudoku solving.

There are some excellent sites that describe the various techniques and patterns useful in solving the puzzles. I always recommend www.angusj.com/sudoku/hints.php mainly because that's a site that contains good basic information but also because I can remember the address easily.

(I'm hoping Cec reads this thread and lists some of the others that I don't remember.)

Tracy
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Times book 1, puzzle 90

Postby Cec » Wed Mar 22, 2006 10:47 am

TKiel wrote:"... (I'm hoping Cec reads this thread and lists some of the others that I don't remember)"

Hi darren,
Firstly, you are correct that the exclusion of candidates in column 1 arising from the naked pair [38] in that column leads to the placement of 9 in cell r6c1(row6 column1). This demonstrates how the identification of naked "pairs" and "triples" doesn't immediately solve those particular cells but leads to the exclusion of those same candidates from other cells which can solve, or assist in solving, those cells.

There are many other sites in addition to angusj's excellent link but I prefer the following additional two - just click on them:
http://www.simes.clara.co.uk/programs/sudokutechniques.htm
http://www.scanraid.com/BasicStrategies.htm

Also, if you click on Here you can read up on the forum's procedures for posting puzzles including candidate grid and the recommended Terminology when defining cells, etc. For example, we refer to "rows" rather than "positions" - as em's saying goes "the chorus sounds better when we all have the same music sheet" or something like that.:)
This is probably enough homework for a while so enjoy your sudoku.
Cec
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Re: Times book 1, puzzle 90

Postby Cec » Thu Mar 23, 2006 11:09 am

cecbevwr wrote:"..There are many other sites in addition to angusj's excellent link but I prefer the following additional two - just click on them:
http://www.simes.clara.co.uk/programs/sudokutechniques.htm
http://www.scanraid.com/BasicStrategies.htm..."

After later noting the ambiguous wording of my above post and to avoid any misunderstanding, the angusj link makes up the "trifecta" for my preferred choice of solving technique links. Apologies to angusj for my poorly worded post.
Cec
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Postby QBasicMac » Fri Apr 07, 2006 11:59 pm

You never came back, so I suppose you are still confused.

Look at column 1. See 38 in r2c1 and r4c1? That means that one of those two cell MUST be 3 and the other MUST be 8. We don't know which, but who cares?

We can therefore eliminate 3 from r6c1 and r7c1.

That gives r6c1=9, right?

After that, it is all singles.

Mac
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Postby TKiel » Sat Apr 08, 2006 1:41 pm

QBasicMac wrote:You never came back, so I suppose you are still confused.


Geez, whenever I post to someone and they don't reply, I always assume my post was so brilliant it answered any question they might ever have about Sudoku and left them so speechless, they couldn't possibly write a reply.

Tracy
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