The New Sudoku Players' Forum

[kiyoshige]

I have the following puzzle I need help with (I know the solution, by process of elimination between either r2c6 and r3c6 being either 4 or 9, but I was wondering if i can solve it without guessing). I would just like the next number and the reason why. Thanks!

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

[Sped]

Code: Select all

 
 *-----------*
 |...|368|..2|
 |783|52.|61.|
 |...|71.|8.3|
 |---+---+---|
 |8..|.4.|2..|
 |.9.|...|.4.|
 |..4|...|..1|
 |---+---+---|
 |5.2|691|...|
 |971|483|526|
 |..8|257|1..|
 *-----------*


Listing the possible candidates:

Code: Select all

 
 *-----------------------------------------------------------------------------*
 | 14      145     59      | 3       6       8       | 479     579     2       |
 | 7       8       3       | 5       2       49      | 6       1       49      |
 | 246     2456    569     | 7       1       49      | 8       59      3       |
 |-------------------------+-------------------------+-------------------------|
 | 8       1356    567     | 19      4       569     | 2       35679   579     |
 | 1236    9       567     | 18      37      256     | 37      4       578     |
 | 236     2356    4       | 89      37      2569    | 379     356789  1       |
 |-------------------------+-------------------------+-------------------------|
 | 5       34      2       | 6       9       1       | 347     378     478     |
 | 9       7       1       | 4       8       3       | 5       2       6       |
 | 346     346     8       | 2       5       7       | 1       39      49      |
 *-----------------------------------------------------------------------------*


The naked pair of 49s you spotted in r2c6 and r3c6 allows the exclusion of the 9s in r4c6 and r6c6. That doesn't help much, though.

But notice another naked pair in row 5. Do the exclusions based on that and watch the singles appear.

[kiyoshige]

I did get this far, but I'm stuck on the exclusions from the naked pair 37. What can I exclude with the naked pair 37? I'm a newbie so please try to be as simple as you can, thanks!

[Sped]

I did get this far, but I'm stuck on the exclusions from the naked pair 37. What can I exclude with the naked pair 37? I'm a newbie so please try to be as simple as you can, thanks!

OK. You spotted the naked pair of 37s in row 5. No other cell in row 5 can be a 3 or a 7. If there were, say, a 7 in r5c3, then r5c5 and r5c7, which form the pair, would both be forced to 3. Impossible.

Ditto if there were a 3 elsewhere in row 5. So all cells in row 5 except that pair can lose their 3s and 7s.

When you do that, a single 7 will appear in column 3, and it's all singles after that.

[kiyoshige]

awesome, thanks!!!