Guardian sudoku - help needed

[mikeymike99]

I've been puzzling over this one (number 1813) for a few weeks now. I've uploaded a picture of it to ebay (because I'm not sure how to upload a pic to answerbank).

In the picture I've included all the numbers I know are correct. I've also filled in every square with two or more smaller numbers which indicates all the numbers which could possibly go in that particular box. This method has helped me solve every sudoku I've ever done, yet it won't help with this one.

If someone could tell me how to solve for one other box I'd be very grateful. I've included letters to help identify each box by a grid reference.

Picture can be found at:
http://cgi.ebay.co.uk...tem&item=170641225839

[bibblebub]

You can't upload pics directly to answerbank but one site for uploading them without needing to register is http://tinypic.com/ - ebay is not really appropriate for this purpose.

[roslyn251254]

What were the original already given numbers?

[merciasounds]

is g/o an 8? looks more like a 5 but you have 5 next to it

[bibblebub]

top right square of top right group is 4

[mikeymike99]

g/o is an 8.
For original numbers you could look at www.guardian.co.uk/lifeandstyle/2011/mar/05/s
udoku-1813-hard

[roslyn251254]

All your numbers are ok so far -
I carried on and got
6 5 3 2 9 8 7 1 4
8 9 7 1 4 3 5 2 6
2 4 1 5 6 7 9 8 3
9 3 6 8 7 5 2 4 1
5 8 4 9 1 2 6 3 7
7 1 2 6 3 4 8 5 9
1 6 5 4 8 9 3 7 2
4 7 8 3 2 6 1 9 5
3 2 9 7 5 1 4 6 8

[merciasounds]

Beat me to it roslyn - I was going to drip-feed him 3 at a time to see if he could finish it!

[mikeymike99]

Hi Rosyln,
Could you tell me how you got the next box? If you could tell me the logic that led to it I'd be *very* grateful as this had been driving me mad for weeks!

[bibblebub]

one way is - after the 4 that i gave earlier look at the 8s

[mikeymike99]

Hi bibblebub,
I'm not sure I follow...I'd filled in all the 4s and top right square of top right group (IK) already has a four in it. Similarly, all the 8s have been filled in.

[bibblebub]

Oh dear, yes you're right - I solved it from the pic you've provided and thought that it was the next step that I took. Sorry.

[roslyn251254]

D2 & D3 can't be 2 (because either D7 or D9 is a 2)
or with your lettering: MB & MC can't be 2 (because either MG or MI is a 2)
Does this help at all?

[mikeymike99]

Thank you Rosyln! Honestly, I've been looking at this on and off for weeks and just didn't see it. I'm sure rest of puzzle will fall into place.

[dzug2]

You can always look up the answer here:

http://www.guardian.c...ndstyle/series/sudoku