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explanations:-
tip 2 - a right pair


This is the 'moderate' puzzle from the Daily Telegraph on 24th. May 2005 which has good examples of what I call a 'right pair'.

While searching for possible cells for a 5 in the column of 3x3 boxes 1, 4 and 7, the 5's in box5 and box7 leave only two possible cells for a 5 in box4; a right pair.

Now that the 5 in row5 must be one of the pair we know that the 5 in the 3x3 box6 must be in row4.

There is only one cell free at c7r4 for the 5.

The solution for the final resting place for the 5 in box4 will have to come later.

This occurs quite often where the solution of a cell is at right angles to the line of search.
c1
c2
c3
  
c4
c5
c6
  
c7
c8
c9
  
 
 
6
 
 
 
8
 
 
 
 
7
 
3
 
r1
 box

1
2
&
3
 
3
box 1 
 
 
 
box 2 
2
 
 
 
8
box 3 
 
6
r2
 
1
 
 
 
 
 
4
 
6		  
 
 
 
r3
 
 
4
 
2		  
 
 
 
3		  
 
 
8
 
1
r4
 box

4
5
&
6
 
box 4 
5?
 
5?		  
 
box 5 
6
 
 
 
box 6 
 
9
r5
 
 
1
 
 
 
5
 
 
 
 
6
 
2
 
r6
 
4 
 
 
 
 
5
 
 
 
 
 
9
r7
 box

7
8
&
9
 
7
box 7 
 
6		  
 
box 8 
3
 
 
 
box 9 
 
5
r8
 
5
 
3
 
1		  
 
 
 
7		  
 
 
6
 
r9



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15th january 2010 © 2014