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12feb06

 
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Nenthorn



Joined: 13 Nov 2005
Posts: 11
Location: Scotland

PostPosted: Mon Feb 13, 2006 10:24 am    Post subject: 12feb06 Reply with quote

I've been sailing through these very hards quite the thing - but now I'm brought back to earth. I cannot for the life of me see what I'm missing here. Can one of you geniuses help me, please?

Here's where I am . . .

900 078 020
010 360 400
300 050 000
080 631 000
001 085 600
600 047 010
100 890 007
804 710 090
769 520 001
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geoff h



Joined: 07 Aug 2005
Posts: 58
Location: Sydney

PostPosted: Mon Feb 13, 2006 11:32 am    Post subject: Reply with quote

Hi Nenthorn,

I'm not sure what values you have as possibilities in the missing squares, but as you appear to know what you are doping , I will assume that you have done basic things such as identifying hidden pairs and unique numbers.

What you can firstly do is consider Row 4. As you can see, the only possibilities for Nr.9 in Row 4 are in cells r4c7 and r4c9. Therefore, you can remove Nr.9 from all other cells in Box No. 6 (cell nos. r4c7 - r6c9).
This is particularly meaningful for cell r6c7 as the remaining possibilities for this cell are then 2,3,5,8.

Now, have a close look at Column 7. There is now a naked quadruplet of 2,3,5,8 in cells r6c7, r7c7, r8c7 and r9c7. This means you can delete these numbers from all other cells in Column 7. This then easily leads to placing the Nr.1 in cell r1c7 and then the Nr.4 in cell r1c4 and the Nr.5 in cell r1c2.

You should be okay from there.

Hope this helps.

Cheers.
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Nenthorn



Joined: 13 Nov 2005
Posts: 11
Location: Scotland

PostPosted: Mon Feb 13, 2006 12:05 pm    Post subject: 12feb06 Reply with quote

Thanks Geoff. I had been staring so hard looking for hidden things I couldn't see the naked one! You're a mate.
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daykart



Joined: 22 Nov 2005
Posts: 10

PostPosted: Mon Feb 13, 2006 12:31 pm    Post subject: Oh my GOODNESS...blind again!!!! Reply with quote

Listen Mr. Smartypants (geoff h),

I would like to echo Nenthorn's sentiments about this puzzle. I too have been going through them like a razor..I only do the very hard ones...but this one "stumpttteddd" me.

Now you come along and in a casual no nonsense sentence say "naked quad" col. 7....I have been looking at this puzzle for hours!!!!!

Thanks buddy...now I can sleep tonight...after I bang my head into brick wall to punish myself for stupidity.

Thanks again

daykart
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dotdot



Joined: 07 Dec 2005
Posts: 29
Location: oberseen

PostPosted: Mon Feb 13, 2006 1:49 pm    Post subject: same thing without seeing a quad Reply with quote

Hallo daykart

I would never see the quad either,
but maybe you would have a better chance at seeing the (complementary) pair instead?

geoff h wrote:
This is particularly meaningful for cell r6c7
i.e. that r6c7 can't be a 9.
Now look where in col7 you can have 7 or 9: not in box9, nor where it crosses row1 or row6. This leaves only r3..4c7 available to hold {7,9}, leaving only r1c7 available for the 1.

This of course begs the question of why you would be looking just there for just that in the first place. No special reason, unless you occasionally check out Glassman pans when stuck.
The Glassman pan based at r7..9c7 requires that the values in the rest of box9 are the same as those in the rest of col7. So the {1,7,9} of box9 should somehow fit into r1..6c7.
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Mon Feb 13, 2006 4:09 pm    Post subject: Another way to look at it Reply with quote

Here's another way to get past the spot Nenthorn illustrated.
Code:
900 078 020
01* 360 4*0
300 050 000
08x 631 000
0*1 085 6*0
600 047 010
100 890 007
804 710 090
769 520 001

There are only two spots for a "7" in row 2, at r2c3 & r2c8. There are only two spots for a "7" in row 5, at r5c2 & r5c8. And there are only two spots for a "7" in the middle left 3x3 box, at r5c2 & r4c3.

If r2c8 = 7 then r5c8 <> 7 ==> r5c2 = 7
If r2c8 <> 7 then r2c3 = 7

Either way there cannot be a "7" at r4c3, so we must have a "7" at r5c2. dcb
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