dailysudoku.com

[gf1701]

A friend sent me a puzzle from a NY Post Sudoku book, and we both got stuck at the same place, which I've shown below. I used the Daily Sudoku Draw/Play feature to give me a hint and it filled in row 6 column 9 with an 8:

+-------+-------+-------+


| . . 1 | 4 3 . | . . . |


| . . 4 | . 7 8 | 6 . 1 |


| . . 7 | . 5 1 | 9 . . |


+-------+-------+-------+


| 4 8 6 | 7 9 5 | 1 2 3 |


| 7 1 3 | 8 2 4 | 5 6 9 |


| 9 5 2 | . 1 . | . 7 ? |


+-------+-------+-------+


| . . 5 | . 4 . | . 1 . |


| 3 . 9 | 1 8 2 | . . . |


| 1 . 8 | 5 6 7 | 3 9 . |


+-------+-------+-------+

I can't figure out how I could have determined that. Can someone explain it to me? Here is the grid with the possibilities I had:

--------------------------------------------------------------------


|8652    962     1  |    4      3       96  |  72      85     752   |


|  52    932     4  |   92      7       8   |   6      53       1   |


| 862    632     7  |   62      5       1   |   9      843      42  |


|-----------------------------------------------------------------


|   4     8      6  |    7      9       5   |   1       2       3   |


|   7     1      3  |    8      2       4   |   5       6       9   |


|   9     5      2  |    63     1       63  |  84       7       84  |


------------------------------------------------------------------


|  62     762    5  |    93     4       93  | 872       1     8762  |


|   3     764    9  |    1      8       2   |  74      54     7654  |


|   1      42    8  |    5      6       7   |   3       9       42  |


--------------------------------------------------------------------

Thanks.

[Marty R.]

There is a naked 42 pair in column 9. Since those two cells with the pair must contain a 4 and 2 in some combination, no other cells in column 9 can contain either a 4 or a 2. Since r6c9 can't have a 4, the only remaining option is the 8.

[gf1701]

Thanks for pointing that out. I don't know why I missed it.

[Marty R.]

You're welcome. I can stare at a puzzle for hours and then finally see something that should have jumped right off the page at me. Happens much more than I'd like.