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Tough Sudoku for 8/April/2009

                 
                 
                 
                 
                 
                 
                 
                 
                 

Choose a number, and place it in the grid above.

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Sudoku Solving Techniques

Submitted by: sudoku lover

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Wagdy, we are enjoying these photos almost as much as you had taking them!
08/Apr/09 12:07 AM
1. Note triples 456 at i289;127 at g6/h45,pair 38 at cg9.Unique possibilities to 35.
2. If c7=6,pair 29 at b78,a8=8=c4,c9=3,c2=9,c1=5,a2=2,h1=3 and column a is devoid of 3. So pair 39 at c27 and UPs to 41.
3. When b5=6,e8=6 and top left box is devoid of 6.The same applies to b5=9.Hence b5=7 and UPs to 81.
08/Apr/09 2:19 AM
1.Start at 22,basic techniques to UP=38
2.WY-style.(89=6)a46-(6)a1=(6-5)c1=(5)c4,=>c4<>8.UP=41
3.(9);b7=df7-e8=e5,=>b5&l t;>9
4.(6);b7=f7-e8=e5,=>b5<>6.UP=81
08/Apr/09 6:48 AM
Step 3,4 also;
3.(9);b78=b5-e5=e8,=>a8<>9
4.(6);b78=b5-e5=e8,=>a8<>6.UP=81
08/Apr/09 7:07 AM
30:12
08/Apr/09 11:11 AM
Alfred! You can't have a pair 39 at C27 because you already know that C2 can't be 3. The fixed 3s at F8 and B4 together with the fixed numbers at A7 and A9 mean that the 3 for that top left square must be in column C (C7 or C9) ergo C2 is not 3 from initial set-up.
08/Apr/09 1:18 PM
Thanks Kate. I missed c2=9 in step 1.Luckily,showing that c7<>6 in step 2 still leads to UP 41.(Note that the finished puzzle has pair 39 at c27).
08/Apr/09 2:17 PM
It does ... not disputing that ... just that it wasn't an issue! Not often I get to make a comment on the Tough!
I use your solutions a lot and find them very helpful.
08/Apr/09 6:22 PM
What a pretty scene, Wagdy. Thanks! (Love those palm trees!)
08/Apr/09 9:52 PM
34:32
11/Apr/09 12:32 AM
1. UP=38
2. (6=5)c1-(5=269)b378 => ~(6)c7. UP=41.
(can't see sotir's revised step 3. here; with 9 in b6 how do you get (9)b78=(b5)?).
3. (9)e5=e8-ab8=b7 & (6)e5=e8-f7=b7, => ~(69)b5 UP=81.
17/May/10 12:17 AM

SE=7.2
09/Sep/10 10:18 PM
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