## I'm stuck, would like help

Post the puzzle or solving technique that's causing you trouble and someone will help

### I'm stuck, would like help

Hello, I'm new here and new to sudoku in general, and I'm stuck with this one. Could someone tell me what I can cross off and why so?

image.jpg (205.66 KiB) Viewed 374 times
NormanvD

Posts: 3
Joined: 05 August 2015

### Re: I'm stuck, would like help

I see a unique rectangle (type 2) and then singles to the end.

JasonLion
2017 Supporter

Posts: 640
Joined: 25 October 2007
Location: Silver Spring, MD, USA

### Re: I'm stuck, would like help

Could you point it out to me? I can't seem to find it
NormanvD

Posts: 3
Joined: 05 August 2015

### Re: I'm stuck, would like help

Code: Select all
`*--------------------------------------------------------------*| 9     1     8      | 2467  247   26     | 47    3     5      || 3     47    2      | 1     9     5      | 8     47    6      || 47    6     5      | 3     8     47     | 1     2     9      ||--------------------+--------------------+--------------------|| 6     5     1      | 27    27    9      | 3     8     4      || 8     47    47     | 5     1     3      | 9     6     2      || 2     9     3      |*48    6    *48     | 5     1     7      ||--------------------+--------------------+--------------------|| 147   3     47     | 9     24-7  126    | 26    5     8      || 5     2     6      |*48+7  3    *48+7   | 4-7   9     1      || 147   8     9      | 246-7 5     126    | 26    47    3      |*--------------------------------------------------------------*`

To explain the Unique Rectangle that Jason mentioned, look at the cells I've marked *. They all contain 48 except for the lower two that contain 48+7.

If neither of these lower two cells were to contain 7 then all 4 cells would contain only 48. This is an impossible arrangement.

The puzzle would have either 0 solutions, or 2 solutions by interchanging the 4's and 8's in the 4 cells. Since most published puzzles are supposed to have exactly one solution the 4 exposed 48's would probably correspond to a 0 solution state.

Either way, one of the 7''s in the lower two * cells must be 7. This means that you can remove 7 from all cells that can see both of these cells. There are 3 of them that I've marked with -7 in the diagram.

You don't say whether you are familiar with Unique Rectangle arguments or just overlooked this one. If not, here are links to two excellent teaching sites that discuss this topic, and a whole lot of other solving techniques.

http://hodoku.sourceforge.net/en/techniques.php

http://www.sudokuwiki.org/Strategy_Families

Leren
Leren

Posts: 3319
Joined: 03 June 2012

### Re: I'm stuck, would like help

Thank you very much for your in depth explanation! I'll was familiar with the unique rectangle but I overlooked this one completely, thanks alot!
NormanvD

Posts: 3
Joined: 05 August 2015

### Re: I'm stuck, would like help

No need to suppose uniqueness:

finned-x-wing-in-columns: n4{c7 c5}{r1 r8} ==> r8c6 ≠ 4, r8c4 ≠ 4
singles to the end
denis_berthier
2010 Supporter

Posts: 1261
Joined: 19 June 2007
Location: Paris