solve

 sudoku

  step 1 2 3 4 5 6 7 8 9 10
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A very easy puzzle to get the idea of how sudoku is solved
Roger Walker
explanations:-
this is step 7


With 4's in r6 and c6 there is only one place for a 4 in box 5 at c4r4 and the new 4 in c4 together with 4's in c6 and r3 fix the 4 in box 2 at c5r2.

Now the new 4 in box 2 with the 4 in c1 fix the 4 box 1 at c2r1.

Row 4 now has only two numbers missing from 1 to 9 and they are 1 and 6. A 6 cannot be in c6r4 because there is already a 6 in c6 so it must be a 1 and consequently a 6 in the remaining space in box 6 at c7r4 .

There is now only one cell left in box 5 which must be ... what?

 

c1
c2
c3
 
c4
c5
c6
 
c7
c8
c9
 
 
4

 4

1
   
5
 
9

6
   
3
 
r1
box

1
2
&
3
 
3
-box 1-
4
 
4
   
4
-box 2-
4
 
4
 
9
- box 3 
5
r2

8
 
 
9
 
7
 
4
 
4
   
 
r3

9

8

3
   
4

2
 
1
 
 
5

7
r4
box

4
5
&
6
 
- box 4 

4
 
8
- box 5 -
7

5
   
- box 6 
9

 
r5

5
 

7
 
?

6

9
 
1
 
8

r6
 

3
 
8
 
1

5
 
  4
6

9
r7
box

7
8
&
9

- box 7 
9

5
 
6
- box 8
 
 
 
box 9 
 

 
r8
 

6

 
9

8

 
5

 

 
r9




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15th january 2010 © 2014