## Problem at first Hard

Advanced methods and approaches for solving Sudoku puzzles

### Problem at first Hard

can anyone help me with the next step

7*5 *1* **9
*6* 8*7 *4*
*** *** ***

938 *** 567
*** 675 ***
657 **8 421

5** *** **4
84* 5*2 *1*
3** *8* *52
HopDunne

Posts: 3
Joined: 28 June 2005

look at row 8 ...you can insert a number...
Arnie

Posts: 49
Joined: 19 May 2005

It is worth noting that this grid, as posted, does not have a solution.
scrose

Posts: 322
Joined: 31 May 2005

Yes, it's a funny thing how a starting grid with no obvious problems on it (duplicated numbers, etc) can in fact have no solutions... but, nevertheless...

(if you want to verify this for yourself, go to http://sudoku.sourceforge.net/ and enter the grid, then click "Evaluate". You can also click "Solve" and the program will fill in as much of the grid as possible before giving up - you can do quite a lot before you have to do that it seems...)
Hammerite

Posts: 44
Joined: 20 June 2005

### Problem at first HArd

Arnie wrote:look at row 8 ...you can insert a number...

To "Arnie " Could you please explain where a number goes in row 8 and your logic to arrive at this?
Bonsai Cec
Cec

Posts: 1039
Joined: 16 June 2005

cecbevwr,

There's only one cell in row 8 that can contain a 7.
Last edited by simes on Sun Dec 11, 2011 2:34 pm, edited 1 time in total.
simes

Posts: 324
Joined: 11 March 2005
Location: UK

### Re: Problem at first Hard

HopDunne wrote:can anyone help me with the next step

7*5 *1* **9
*6* 8*7 *4*
*** *** ***

938 *** 576
*** 675 ***
657 **8 421

5** *** **4
84* 5*2 *1*
3** *8* *52
Sorry everybody,top row in block six had an error which i have now corrected(576 instead of 567)
HopDunne

Posts: 3
Joined: 28 June 2005

Look at where the 4's can go in row 3.
After making some eliminations, you can fill some cells in block 5.
scrose

Posts: 322
Joined: 31 May 2005

cecbevwr,

simes's answer is spot on. Is that clear?

Arnie
Arnie

Posts: 49
Joined: 19 May 2005

HopDunne wrote:In row 3, box 1 or 3 can only contain a 4. In row 1, box 4 or 6 and row 8 box 4 or 6, this does not help me with 124 in block 5, what do you think ?

Your terminology is a little confusing. Instead of saying "row 3, box 1 or 3", say "row 3 column 1 or row 3 column 3", or abbreviated as "r3c1 or r3c3". The term "box" usually refers to one of the 3x3 subgrids. Wayne has suggested some common terms that we should try to use to avoid confusion amongst each other.

First, to clarify, I think you meant to write row 9, not row 8.

For now, ignore all other rows: focus only on row 3 and where the 4's can go in it. You may have already noticed what I am about to explain, but just in case you haven't...

The only candidate 4's in block 1 are located in row 3. This means that the 4 that is located in row 3 must be located in block 1. That means that there cannot be any 4's in row 3 in blocks 2 or 3. So in this puzzle, you can eliminate the candidate 4's from r3c4, r3c5, and r3c6.

Having made those eliminations, where can you put a 4 in column 5?

(If interested, you can read more about the technique I used.)
scrose

Posts: 322
Joined: 31 May 2005

### Problem at first Hard

scrose wrote:
HopDunne wrote:In row 3, box 1 or 3 can only contain a 4. In row 1, box 4 or 6 and row 8 box 4 or 6, this does not help me with 124 in block 5, what do you think ?

Your terminology is a little confusing. Instead of saying "row 3, box 1 or 3", say "row 3 column 1 or row 3 column 3", or abbreviated as "r3c1 or r3c3". The term "box" usually refers to one of the 3x3 subgrids. Wayne has suggested some common terms that we should try to use to avoid confusion amongst each other.

First, to clarify, I think you meant to write row 9, not row 8.

For now, ignore all other rows: focus only on row 3 and where the 4's can go in it. You may have already noticed what I am about to explain, but just in case you haven't...

The only candidate 4's in block 1 are located in row 3. This means that the 4 that is located in row 3 must be located in block 1. That means that there cannot be any 4's in row 3 in blocks 2 or 3. So in this puzzle, you can eliminate the candidate 4's from r3c4, r3c5, and r3c6.

Having made those eliminations, where can you put a 4 in column 5?

(If interested, you can read more about the technique I used.)
Thanks scrose i should have seen that one, i am new to the game so i will learn the proper terminology or common terms so as not to be confusing everyone, thanks again, Slainte.
HopDunne

Posts: 3
Joined: 28 June 2005

### Problem at first hard

My apologies to simes, arnie, Animator. I now feel an idiot in not recognizing earlier that there's only one cell in row 8 that can contain a 7.
I'm new to this including the procedure for sending posts. Sorry again for my silly mistake.
Bonsai Cec
Cec

Posts: 1039
Joined: 16 June 2005

If I apologised every time I made a mistake in Sudoku, ....!!

This forum is where you can post questions/puzzles that have you stumped/or where you fail to understand the logic in other threads. Long may that continue.

Please don't feel the need to apologise. Hope you find this forum as useful, approachable and supportive as I do.

Regards,

Arnie
Arnie

Posts: 49
Joined: 19 May 2005