dailysudoku.com

[eddieg]

A little "Help!" required - Here's where I am at.

000 507 006
000 064 070
076 002 040

465 981 327
030 756 010
197 423 568

610 240 700
000 370 601
750 618 000

The hint is for a 4 in R1C2.

From doing my sweeps I know that R1C2 or R1C3 needs to be a 4. I also see that my only possibilities for a 4 in column 2 are in rows 1 and 8. I just don't see how the possibilities of 2 and 8 being eliminated in R1C2 give me the result of 4 in this particular cell.

Thanks in advance for any help.

[David Bryant]

Hi, eddieg!

-- The "8" in column 8 must appear in the bottom right 3x3 box.

-- Therefore the only possibilities at r1c8 are {3, 9}. This pairs up with the {3, 9} in r1c5, so the values {3, 9} can be eliminated in the rest of row 1.

-- Look at the top left 3x3 box. The possibilities at r1c1 are {2, 3, 8, 9}. At r1c2 they're (2, 4, 8}, and at r2c2 they're {2, 8}. But when you eliminate the {3, 9} at r1c1 you'll see the {2, 8} pair in r1c1 & r2c2, leaving "4" as the only possibility at r1c2.

-- There's also a {2, 8} in r5c1. So once you've identified the {2, 8} at r1c1 you'll have a pair in column 1, from which you can set r8c1 = 9. This is what I actually saw when I hit this spot in the puzzle this morning -- I didn't notice the {2, 8} at r2c2 until a little later. dcb

[eddieg]

Thanks again.

I was reading "to much" into the "28" pairs in that area of the puzzle, and was thinking that there was some more "advanced" technique involved.

[fkhalili2002]

Hello Guys, I am kind of a newby with Sudoku but I'm doing alright so far. I just need a little help as I am just one step behind eddieg when he posted the original request for help.

Here is where I am:
000 507 006
000 064 070
076 002 040

465 981 327
030 756 010
197 423 568

610 240 700
000 370 601
700 618 000

I don't see the logic about how "5" ends up in R9C2 and it's driving me nuts. Would you please explain the reasoning?

Thanks.

[Marty R.]

[David Bryant]

Hi, fkh! Welcome to the forum.

This is a case of "row on 3x3 block interaction."

-- Observe, first, that there are 5 open cells in row 8. Three of these lie in the bottom left 3x3 box, and only two lie outside that box (r8c6 & r8c8).

-- Notice next that neither "2" nor "4" can lie in r8c6 or r8c8. So both the "2" and the "4" in row 8 must lie in the bottom left 3x3 box.

-- Now think about the apparent possibilities at r9c2. It looks as if it could be {2, 4, 5}. But it can't be "2" or "4", because those have to lie in row 8 in this box, by our reasoning above. So the only value left is "5". dcb

[fkhalili2002]

Thank you Marty R. and David Bryant for your help . I now see the light and how you got there . And yes Marty, it restored my sanity (at least temporarily) until I get to the next tough one and there will be a lot of tough ones while I am learning the techniques and thought processes that are probably as easy as drinking water for your guys.

Thanks again and hopefully I won't bother you any more for this puzzle. fkh

[Marty R.]

[sdtibbs]

I am confused with the explanation of the May 26th puzzle. I do not see how there is not an option of a 5 in r2c1 or r3c1. It was stated that the possibilities of r1c1 were 2,3,8,9, and there was not an option of 5. I find that the only place a 5 can go is in either r2c1 or r3c1. I solved the problem with the 5 in r3c1. Please help. :?

[fkhalili2002]

I am sorry SDT, maybe I am missing something. You said that "it was stated that the possibilities of r1c1 were 2,3,8,9 and there was not an option for 5". This is a true statement stated by David Bryant, as r1c4 contains a "5". However, if you really meant r2c1 or r3c1, I don't believe anyone has said these cells can not have a "5". In fact running sweeps shows the possibility of having "5" in these cells, and your assessment and solution is correct. Hope this helps, if not please let me know. fkh

[sdtibbs]

Thanks for getting me straight. Had my r and c wrong; had been working on the puzzle for awhile and got cross-eyed. thanks again.