## stuck in this one

Post the puzzle or solving technique that's causing you trouble and someone will help

### stuck in this one

Here is the original puzzle

Code: Select all
` *-----------* |.8.|...|.23| |..5|.31|...| |74.|...|...| |---+---+---| |39.|...|...| |.2.|...|.8.| |...|4..|.79| |---+---+---| |4.2|..7|9..| |6..|1.9|..7| |9..|2..|.6.| *-----------*`

so far

Code: Select all
` *-----------* |189|...|.23| |265|.31|...| |743|...|...| |---+---+---| |39.|...|..2| |52.|...|.8.| |816|4..|.79| |---+---+---| |4.2|..7|9..| |6.8|1.9|2.7| |97.|2..|.6.| *-----------*`

Now from what the solvers tell me, r1c7 [4567] and r9c7 [3458] have a pair Hidden pair that lets me ~3 r9c7, which releases the next set of numbers. The question is why?

Thanks.

Aram

Posts: 6
Joined: 05 September 2006

A much simpler approach is to note that c8 has threes only at r7 and r8.
That means r7c8 is 3 or r8c8 is 3. r9c7 cannot be three.

There is a similar exclusion, look at column 7 in the middle box.
The only threes in the box are in column 7, thus there can be no threes
in c7 in the box above and below.

As to the hidden 45 pair, I don't see it nor can I disprove it.
wapati
2010 Supporter

Posts: 527
Joined: 13 September 2006
Location: Brampton, Ontario, Canada

Amirzadeh wrote:r1c7 [4567] and r9c7 [3458] have a pair Hidden pair

There is no hidden pair in those cells. What you have is: a naked single in r9c3 ("1"), and locked candidates in box 6 ("3"), which allow us to exclude "3" from r9c7. The type-1 UR then later solved the puzzle.

Carcul
Carcul

Posts: 724
Joined: 04 November 2005

wapati wrote:A much simpler approach is to note that c8 has threes only at r7 and r8.
That means r7c8 is 3 or r8c8 is 3. r9c7 cannot be three.

There is a similar exclusion, look at column 7 in the middle box.
The only threes in the box are in column 7, thus there can be no threes
in c7 in the box above and below.

As to the hidden 45 pair, I don't see it nor can I disprove it.

This did the trick for me. I should have noticed that '3' was only present in c7r456 so that it would ~3 c7r789.

Thank you.