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 sudoku

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explanations:-
this is step:- 15


A pair of possible 9's in box 2

In column 4, if the two bottom cells in box 8 have to be 3 and 4 then the only cell left is in box 2 which therefore must be a 2.

As we know 1 can only be in two cells in box 2 we also find 1

 


In box 8 there are only two cells empty so each must be 3 or 4

c1
c2
c3
 
c4
c5
c6
 
c7
c8
c9
 
 
 
3
 
 
5
 
 9
 
 
8
 
1
 
r1
box

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

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

7
8
&
9
 
box 7 
9
 
3 4 
box 8 
8
 
6
 
 
box 9 
 
1
r8
 
 
6
 
1
 
 3 4
 
9
 
2
 
 
 
8
 
r9



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15th january 2010 © 2014