# sudoku

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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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