whats a guesser?

[ArchiveGuest]

(This post was originally by juggle7)
Hi, I'm new and very inerested in this forum. I'm having a debate with my brother about a puzzle, and the definition of what I call a guesser. Is it true that if you get to a point in a puzzle that 2 or more numbers can work in every available empty square that you must now start guessing? Please look at the following grid and tell me if it can be proven without a guess that the number 1 goes in the box address of 1-1. Thanks

090 536 072
037 000 650
562 700 903

009 287 536
306 050 007
705 163 009

901 370 265
653 000 700
270 605 390

[Howard]

Yes, its possible to make progress to prevent it from having multiple solutions. (That's what you call a guesser, I think :) )

The boxes are numbered
123
456
789

If you look in box 4, you'll see that the only two cells with an 8 as a possible candidate lie in a (vertical) line. That means that the 8 *has* to be in one of those places, so that entire line can't have any 8s in any other boxes (1 or 7). That means you can rule out 8 as a candidate in r7c2, leaving that with just 4 as its only candidate.

http://www.sudokuoftheday.com/image/image.php?size=230&sg=(148)W9(48)536(148)72(148)W37(489)(1249)(12489) 65(148)5W627(14)(148)9(148)3W(14)W(14)W9287536W3W( 1248)W6(49)5(49)(148)(1248)7W7W(248)W5163(48)(248) 99X(48)137(48)2656W53(489)(1249)(12489)7(148)(148) 2W7(48)6(14)539(148)

The rest from there is easy :)

[Howard]

Oh, and it isn't a 1 that ends up at the top left ;)