dailysudoku.com

[JOn1606]

Hi
Could someone please tell me how the hint option put a 5 in Column 6 Row 2 in todays (24-7-2006) sudoku puzzle.
Thanks
Jonathan

[Bluewitch]

When i was at the stage of putting the 5 in column 6 row 2 I had the following numbers completed:

x x 3 1 x x 5 4 x
x x x x 4 X 3 9 x
4 5 2 x 3 x 1 7 x
3 2 x x 1 x 4 8 7
x 1 8 4 x 2 9 6 3
6 x 4 x 8 x 2 5 1
x x x x 9 4 7 3 5
x 4 x 3 x 1 8 2 9
x 3 x x x 7 6 1 4


Column 6 row 1 can only be 6 or 8 (as 9 must be in Row 1 column 1 or 2)
Column 4 row 3 can only be 6, 8 or 9
and Column 6 row 3 can only be 6, 8 or 9
Therefore you have a hidden triplet and can eliminate 6 and 8 from column 6 row 2, thus leaving the 5.

Hope that helps!
xx.

[David Bryant]

That's a good explanation, xx! Here's another way to look at it.

0 0 3 1 0 0 5 4 0
0 0 0 0 4 0 3 9 0
4 5 2 0 3 0 1 7 0
3 2 0 0 1 0 4 8 7
0 1 8 4 0 2 9 6 3
6 0 4 0 8 0 2 5 1
0 0 0 0 9 4 7 3 5
0 4 0 3 0 1 8 2 9
0 3 0 0 0 7 6 1 4

Because of the "2"s and "7"s highlighted above (in row 3 and column 6), it's clear that the hidden pair {2, 7} must lie in r1c5 & r2c4. This leaves r2c6 as the only cell in the top center 3x3 box that can possibly contain a "5". dcb

[David]

There also appears to be a unique rectangle based on R5C15 (7/5 and 7/5) and R8C15 (7/5 and 6/5) which forces a 6 in cell R8C5 ??