The New Sudoku Players' Forum

[tonyjer]

Hi Everyone

Still new so will this will probably be breathtakingly obvious but here goes.

Angus J's illustration of hidden quads is

169/279/38/13458/345/1345/458/257/4678

It appears that the quads lurking here are in the first, second third and fourth boxes. As there have to be 4 candidates and they have to be restricted to 4 cells:

Am I right in identifying 2679?

If so the second box is naked and I didn't think such mixing was possible.

Be grateful for any advice for a novice.

Thanks

Antonio, Anna y Eduardo Felipe

[ravel]

169/279/38/13458/345/1345/458/257/4678
...
Am I right in identifying 2679?

Yes, 2679 can go only into columns 1,2,7 and 8 (of this row). So they are restricted to these numbers and you can eliminate 1 from column 1 (leaving 69), 5 from column 8 (leaving 27) and 48 from column 9 (leaving 67).

[MCC]

If so the second box is naked and I didn't think such mixing was possible.

If the four cells that make up a quad contain only the four candidates then it is classified a naked quad.

If any of the four cells that make up the quad contain an extra candidate or two, then that quad is hidden, even if only one of the cells has the extra candidate/s.

MCC

[tarek]

hi tonyjer,

this example comes from another thread........

Try row 3,,, there is a naked quad & at the same time there is a hidden double...

both of them have the same end result....... I'm sure if you find both, you'll never have a problem with them afterwards...

Code: Select all

*-----------------------------------------------------------------*
| 378    3689   2     | 1      689    36    | 4      37     5     |
| 348    3468   5     | 7      2468   2346  | 39     1      2369  |
| 1      3469   67    | 26     2469   5     | 8      237    2367  |
|---------------------+---------------------+---------------------|
| 6      1      8     | 5      3      47    | 2      9      47    |
| 235    23     9     | 8      246    2467  | 357    34567  1     |
| 235    7      4     | 9      1      26    | 35     356    8     |
|---------------------+---------------------+---------------------|
| 278    268    3     | 4      2567   1     | 579    2578   279   |
| 2478   5      67    | 236    267    9     | 1      23478  2347  |
| 9      24     1     | 23     257    8     | 6      23457  2347  |
*-----------------------------------------------------------------*

Tarek

[tonyjer]

Apologies for the delay in acknowledging but have been unwell

Many thanks again

Antonio, Anna y Eduardo Felipe