After you have completed the basic exercise
above,
here is another strategy to consider.
The possibilities (in green)
for nines in the fourth row are in the last two
cells
|
7 |
9 |
|
|
2 |
4 |
|
|
|
| |
5 |
6 |
|
|
|
|
|
|
| |
|
2 |
9 |
|
|
|
|
|
|
4 |
1 6
7 |
3 |
2 |
8 |
1 6
|
5 |
1 6
7 9 |
1 6
7 9 |
| |
|
|
|
|
|
9
. |
9
. |
9
. |
| |
|
|
|
|
|
9
. |
9
. |
9
. |
| |
|
|
|
|
9 |
|
|
|
Because you must have a nine in the fourth row
in the shaded box,
you cannot have a nine in the other rows of that
shaded box (the red nines).
Another strategy:
What can you guess about the middle rows of the
two shaded boxes?
Again, the possibilities for the middle row of the
middle box are in green:
| |
5 |
|
6 |
1 |
8 |
|
5 |
|
| |
|
|
2 5
|
2 5
9 |
2 9
|
|
|
|
| |
2 |
|
7 |
3 |
4 |
|
6 |
|
Answer::
What can you guess about the middle rows of the
two shaded boxes?
Again, the possibilities for the middle row of the
middle box are in green:
| |
5 |
|
6 |
1 |
8 |
|
7 |
|
9 |
9 |
9 |
2 5
|
2 5
9 |
2 9
|
2 5
9 |
2 5
9 |
2 5
9 |
| |
2 |
|
7 |
3 |
4 |
|
6 |
|
Answer:
In the middle box, only three numbers
2 5 9 are possible, and there are only three spaces
available. Therefore, those possibilities
are not possible in the spaces in the rows of the
other boxes.
Since there already is a 5 and 2 in the
left-hand box, that eliminates 2 and 5 in the
middle row. 9
is not possible in its middle row since a nine
must be in that row of the middle box..
In the right-hand shaded box, all three
2
5 9 are not possible in the
middle row and must be options in its empty spaces.
Websites on Sudoku:
What's a Pappacom
puzzle? What are symmetrical clues?
Computer-generated or hand-constructed
puzzles?
-
Wikipedia
All about Sudoku, strategies, etc.
-
Natural
Maths Sudoku
Use Microsoft Excel to help you learn to solve Sudoku
-
Websudoku:
"Billions" to work online, four levels of difficulty,
with checking feature
-
Sudoku . com. au
Australian Sudoku solving on line with a picture for a reward!
Flash exercise
contributed by
Matt Schiller and Dr. Brad
Hokanson, Interactive Media (DHA 4384) School of
Design, University of Minnesota.
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