# sudoku

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explanations:-
tip 3 - the third column

This has an example of what I call 'the third column'.

The game is part done and we are looking at 3's here and from this information we can find the 3 in c5r4.

Looking at Box2, we can see that the 3 in row1 means that a 3 must be in column4 or column6 of Box2.

Looking at Box5, we can see that the 3 in row6 means a 3 must be in row4 of Box5.

Looking at Box8, the 3 in row9 means that a 3 must be in c4 or c6 of Box8.

Now there's that column4 and 6 again!

So logically, if a 3 must be in c4 or c6 of Box2 and Box8 there cannot be a 3 in those columns in Box5. A 3 must be in the third column of Box5 - column5.

As we have already proved that a 3 must be in row4 of Box5 and it cannot be in c4 or c6, therefore a 3 must be in c5r4.

This is the 'tough' puzzle from the Daily Telegraph on 15th. October 2009
(ok, in this instance, the 3 can also be found by the fact that there is only one cell left for it in c5 but this is not always the case with this tip)

c1
c2
c3

c4
c5
c6

c7
c8
c9

7
2     3 9
r1
box

1
2
&
3
 box 1

 3?
 box 2
1
 3?

 box 3
r2

 3?
4
 3?
2
r3
7 9
 3?
 3?
 3?
8
r4
box

4
5
&
6
2
 box 4
8   4
 box 5
7
6
 box 6
5
r5
3 2
r6
2
 3?
9
 3?
6
r7
box

7
8
&
9
 box 7

 3?
 box 8
6
 3?

 box 9
r8
3 1     9 8
r9
 ___________________________________ [ contact me, Roger Walker ] 15th january 2010 © 2012