solve

 sudoku

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explanations:-
this is step:- 9


Back to working the board looking for possible pairs of cells. 3's show in box 5.

 

7* possibles have to be as shown in box 5, no other spaces left!
But 7's can only be in r6 of box 4.
Therefore a 7 cannot be in row 6 for box 4 and box 5 so it must be a 7 in c5r4 in box 5
c1
c2
c3
  
c4
c5
c6
  
c7
c8
c9
  
 
 
3
 
 
 
5
 
 
 
 
8
 
1
 
r1
 box

1
2
&
3
 
1
box 1 
 
 
 
7
box 2 
6
 
 
 
box 3 
9
 
r2
 
4
 
 
 
 1
1 
 
 
 
 
 
r3
 
8
 
4
 
3		  
 
9
 7*
7
 
5		  
 
1
 
 
6
r4
 box

4
5
&
6
 
box 4 
1
 
 
 
6
3
3 
 
 
box 6 
7
 
8
r5
 
6
 7
7 
 
 
8
 7*
 
1		  
 
9
 
3
 
r6
 
 
 
 
 
 
5
 
 
 
 
 
9
r7
 box

7
8
&
9
 
box 7 
9
 
 
 
box 8 
8
 
6		  
 
box 9 
 
r8
 
 
6
 
1		  
 
 
9
 
2		  
 
 
8
 
r9



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15th january 2010 © 2014