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July 8

 
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Lynne_H



Joined: 13 Jul 2007
Posts: 3

PostPosted: Fri Jul 13, 2007 12:27 am    Post subject: July 8 Reply with quote

The hint says a 3 in R4C1. Can someone tell me why?

[code]
+---------+-------------+-----------+
| 13 13 2 | 6 9 58 | 458 7 48 |
| 9 7 4 | 358 358 1 | 58 6 2 |
| 8 6 5 | 7 4 2 | 9 3 1 |
+---------+-------------+-----------+
| 13 5 9 | 48 6 478 | 147 2 347 |
| 6 4 8 | 2 17 3 | 17 9 5 |
| 2 13 7 | 9 15 45 | 6 8 34 |
+---------+-------------+-----------+
| 7 8 1 | 35 35 6 | 2 4 9 |
| 4 2 3 | 1 78 9 | 78 5 6 |
| 5 9 6 | 48 2 478 | 3 1 78 |
+---------+-------------+-----------+


Thanks,
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Fri Jul 13, 2007 2:02 am    Post subject: Re: July 8 Reply with quote

Lynne_H wrote:
The hint says a 3 in R4C1. Can someone tell me why?



Just a guess, but an XY-Wing at R1C6, R1C9, and R6C6 eliminates the <4> at
R6C9, which forces a <1> at R6C2, which forces a 3 at R4C1. I'm not sure why
it wouldn't call out R6C9 first, but all three cells are tightly linked.
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Fri Jul 13, 2007 3:05 am    Post subject: Reply with quote

Lynne_H,

First a little housekeeping using that 48 Naked Pair in C4.
Code:
+---------+-------------+-----------+
| 13 13 2 | 6   9   58  | 458 7 48  |
| 9  7  4 | 35  358 1   | 58  6 2   |
| 8  6  5 | 7   4   2   | 9   3 1   |
+---------+-------------+-----------+
| 13 5  9 | 48  6   478 | 147 2 347 |
| 6  4  8 | 2   17  3   | 17  9 5   |
| 2  13 7 | 9   15  45  | 6   8 34  |
+---------+-------------+-----------+
| 7  8  1 | 35  35  6   | 2   4 9   |
| 4  2  3 | 1   78  9   | 78  5 6   |
| 5  9  6 | 48  2   478 | 3   1 78  |
+---------+-------------+-----------+

There is an XY-Wing with pivot R1C6 that removes <4> from R6C9, leading immediately to <3> at R4C1. However, a better Hint would have been <3> at R6C9. That's the most direct that I can see.

Even without this XY-Wing, the puzzle succumbs totally to the 35 UR in C45 [R2C5 must be 8].
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Sat Aug 11, 2007 2:09 am    Post subject: Reply with quote

Asellus wrote:
... There is an XY-Wing with pivot R1C6 that removes <4> from R6C9, leading immediately to <3> at R4C1. ...


Asellus — Thanks for that. I had done a little more housekeeping with a couple of simple and obvious x-wings, resulting in a tidier c7, thus

Code:
+---------+------------+----------+
| 13 13 2 | 6  9   58  | 45 7 48  |
| 9  7  4 | 35 358 1   | 58 6 2   |
| 8  6  5 | 7  4   2   | 9  3 1   |
+---------+------------+----------+
| 13 5  9 | 48 6   478 | 14 2 347 |
| 6  4  8 | 2  17  3   | 17 9 5   |
| 2  13 7 | 9  15  45  | 6  8 34  |
+---------+------------+----------+
| 7  8  1 | 35 35  6   | 2  4 9   |
| 4  2  3 | 1  78  9   | 78 5 6   |
| 5  9  6 | 48 2   478 | 3  1 78  |
+---------+------------+----------+


However, that UR was so obvious, shouting at me "Drop your standards — you know that that there is a unique solution", that I failed to see this xy-wing.

Ho hum.

Glassman Cool
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