Unique rectangle type 3

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Unique rectangle type 3

Postby Sudoku123456789 » Thu Oct 19, 2017 5:01 pm

Got stuck...

Found a Unique rectangle type 3 on 25C3R12 and 25C7R12 With addition 34 making naked pair with 34R6C7.
Ecusion of 3&4 in that unit leads to stte, But unvalid puzzle solution.

Question: is my approach valid/did I make a mistake?
In addition: other manners to solve?


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Re: Unique rectangle type 3

Postby champagne » Thu Oct 19, 2017 5:12 pm

unhappily you have a wrong assignment in your grid
forget r7c2=1 and in box 6 you have r5c8=8
Last edited by champagne on Thu Oct 19, 2017 5:15 pm, edited 1 time in total.
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Re: Unique rectangle type 3

Postby Sudoku123456789 » Thu Oct 19, 2017 5:13 pm

I know I should use Keith's principle, But when I'm stuck the only thing that sometimes helps me is by filling all cell candidates and look for patterns. Is this a rookie mistake?
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Re: Unique rectangle type 3

Postby Leren » Thu Oct 19, 2017 7:42 pm

The puzzle in line format : .3..............181.6...7...7...49...2.6....5..128....9..........7.1864.....95...

Here is where you should be after basic moves (note r7c2 is 18, not 1 as in your diagram - in fact in the solution it is 8. Also you missed a BoxRow intersection 3 in r6c789 that removes 3's from other cells in Box 6 and solves r5c8 = 8):

Code: Select all
*---------------------------------------------------*
| 478 3   *25  | 1589 2457   127  |*25+4  2569 246  |
| 47  49  *25  | 59   234567 2367 |*25+34 1    8    |
| 1   489  6   | 589  2345   23   | 7     2359 234  |
|--------------+------------------+-----------------|
| 368 7    38  | 15   35     4    | 9     26   126  |
| 34  2    9   | 6    37     137  | 1-4   8    5    |
| 5   46   1   | 2    8      9    |#34    367  3467 |
|--------------+------------------+-----------------|
| 9   18   348 | 47   26     26   | 158-3 357  137  |
| 2   5    7   | 3    1      8    | 6     4    9    |
| 368 168  348 | 47   9      5    | 128-3 237  1237 |
*---------------------------------------------------*

There is a Type 3 UR (25) in r12c37 with extra digits 34 in the Roof cells. The 34 bi-value helper cell r6c7 creates an effective naked pair 34 in r126c7 so you can remove 3 and 4 from other cells in Column 7, which solves the puzzle.
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