Sudoku%20How%20To

1
Examining the top three rows first
The number 5 appears in row one and row three.
Row two requires a 5. It has to be located in the
middle 3x3 box.
Two possible locations for 5 in centre box
The centre column already has one 5 so it cannot
be above the 8.
Thus, it has to be above the 9 on the second row
2
Examining the top three rows first 5 appears in
row one and row three.
Row two requires a 5. It has to be located in the
middle 3x3 box.
Two possible locations for 5 in centre box
The centre column already has one 5 so it cannot
be above the 8.
Thus, it has to be above the 9 on the second row
3
Now scan down the three central columns
4
Now scan down the three central columns
The second and third columns already have the
number 5 - but the first column also needs a 5.
A 5 has to be located in the lower 3x3 grid box
as the two above already have 5 in them.
The bottom row of nine boxes has a 5 already so
it cannot go in row 9.
Thus, 5 has to go just above the 2 on the first
row of the lower middle 3x3 grid box.
5
Now examine the central three rows - row 4 to row
6.
The number 2 appears in rows 5 and 6 but not in
row 4
?
Fill in the number 2 in row 4 of the central 3x3
grid box.
But Column 4 has a 2 already
Thus, the 2 in row 4 has to go above the 4 in the
central box
6
Now examine the central three rows - row 4 to row
6.
The number 2 appears in rows 5 and 6 but not in
row 4
Fill in the number 2 in row 4 of the central 3x3
grid box.
But Column 4 has a 2 already
Thus, the 2 in row 4 has to go above the 4 in the
central box
7
Continue scanning across and down the columns and
grids filling in the easy numbers.
It can help to systematically go through the
numbers 1 to 9 in sequence for each horizontal
and vertical group of three sub-grids.