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Steve
Joined: 04 Aug 2005 Posts: 3 Location: Leicester

Posted: Mon Aug 08, 2005 12:09 pm Post subject: Why is it a 9? 


Code: 
458 .9. 621
.6. 185 ...
.1. 4.. 8.5
879 614 .5.
134 ... 768
625 .3. 914
.86 ..1 ...
.4. 27. .8.
79. ... .3.

The DRAW function gives the hint R8C6=9. Given that, everything else is easy. But I can't figure out why it should be a 9.
Any ideas? 

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Katie
Joined: 05 Aug 2005 Posts: 13 Location: London

Posted: Mon Aug 08, 2005 3:32 pm Post subject: 


Given that R8C6 can be only be a 3, 6, or 9.
If =3, then R8C3=1, R8C1=5 leaving R8C7 with no option, as can only = 1 or 5.
If =6, then R3C6=2, R3C5=6, R5 centre = 5,2,9, R9C4=8, leaving R9C6=6, which impossible.
Thus the only option is 9.
No doubt someone will find a quicker and easier solution to this. 

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bird316 Guest

Posted: Tue Sep 20, 2005 8:33 am Post subject: Interview 


So when will w know more [^] 

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chobans
Joined: 21 Aug 2005 Posts: 39

Posted: Tue Sep 20, 2005 4:23 pm Post subject: 


I don't know if this is easier but I'll make the solution more logical.
r1c4 and r1c6 both only can be 3 or 7. So you can eliminate 3 and 7 from other cells in box 2(r1c4r3c6) and get 2 or 6 in r3c6.
row 8: r8c1  {3,5}, r8c3  {1,3}, r8c7  {1,5}.
That makes it a naked triple, so you can eliminate 1,3 and 5 from other cells in row 8. So r8c6 becomes {6,9}.
At this point, you can say r7c4 can only be a 3 since that's the only place in box 8 where 3 can go.
column 6: r3c6  {2,6}, r5c6  {2,9}, r8c6  {6,9}
Again, a naked triple. So you can eliminate 2,6 and 9 from other cells in column 6. So r9c6 becomes 8 after elimination. You'll eventually get a 9 at r8c6 after simple elimination now.
So I guess the system should've given you a 3 at r7c4 first. But since you asked as how you can get a 9 at r8c6... 

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