## Don't understand hint; help!

Everything about Sudoku that doesn't fit in one of the other sections

### Don't understand hint; help!

I'm running a program (Simple Sudoku) that can generate a hint if you are stuck. When I do this, I always try to understand why the action is allowed. In this case, I cannot. If anyone can explain why the 3's can be dropped from col. 2,4,9 of row 7, I'd be most appreciative...

215|.4.|..8
987|.53|.4.
643|...|.5.
-----------
1..|.78|56.
579|.1.|82.
.6.|5..|..7
-----------
...|...|47.
.9.|7..|..5
7..|.6.|982

{2} {1} {5} {69} {4} {679} {367} {39} {8}
{9} {8} {7} {126} {5} {3} {126} {4} {16}
{6} {4} {3} {1289} {289} {1279} {127} {5} {19}
{1} {23} {24} {2349} {7} {8} {5} {6} {349}
{5} {7} {9} {346} {1} {46} {8} {2} {34}
{348} {6} {248} {5} {239} {249} {13} {139} {7}
{38} {235} {1268} {12389} {2389} {1259} {4} {7} {136}
{348} {9} {12468} {7} {238} {124} {136} {13} {5}
{7} {35} {14} {134} {6} {145} {9} {8} {2}
Prometheus bound

Posts: 2
Joined: 30 July 2005

Press "control 3" to fliter candidate 3s.

Code: Select all
`The 3 in row 4 must be in column 2 or 4 or 9.The 3 in row 5 must be in column . . .4 or 9.The 3 in row 9 must be in column 2 or 4.`

No matter how you place the 3s in these three rows, there will be one in each column. Therefore, you may removed all other candidate 3s from those three columns.
tso

Posts: 798
Joined: 22 June 2005

Ok, I feel silly. Thanks
Prometheus bound

Posts: 2
Joined: 30 July 2005

Same difficulty. Can someone explain the 6 provided as a hint in r8c9?
Code: Select all
`..2.568..51..7..4.......5..63.249.58.5.6.7...2...15.64925.6.487.4.598.26.4.7249.5`

Thanks.

cho
edit: found it - thanks
cho

Posts: 18
Joined: 07 August 2005

Cho, your grid isn't correct. Two 4s in column 2 and two 4s in row 9.

Simes
simes

Posts: 324
Joined: 11 March 2005
Location: UK

For this puzzle to have a unique solution, you must get rid of the 4 at r9c2 and place an 8 at r9c3.

G
george-no1

Posts: 150
Joined: 20 May 2005

Sorry, a bit of transpositioning there. For any interested row 9 should have been |.68|724|9.5|. George is quite correct. Figures I'd leave out the 8 that I was overlooking for an hour.

cho
cho

Posts: 18
Joined: 07 August 2005