One of our visitors (Phyllis) asked about the puzzle posted on October 13. Now, this puzzle definitely doesn’t need any trial and error to be solved – in fact it’s only rated as “thinker”. However, it requires a technique that in the new version of Perfect Sudoku will be called “complex innies/outies”. It is basically the same as regular innies/outies except that you should look for a more complex “structures” than just single nonets/rows/columns.
Here is more precisely what I’m talking about. This image shows how far you should get using standard techniques:
(click to download or rightclick to save the image)
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To see the solution to this puzzle click here
Have a look at the “structure” that is outlined in red. It consists of 3 nonets and therefore the sum of all numbers in it should be 3*45 = 135. And if you pay some attention you will see that there is an innie for this whole structure in the bottom left corner of nonet number 9. Therefore it’s value must be 135(10+11+14+18+4+13+8+28+13+7) = 135126 = 9.
From there a few more innies/outies spawn and then you should be able to solve this baby with standard sudoku techniques (namely – naked/hidden/match pairs).
Check the Solving tips section for more details on innies/outies.
3 Comments
Adding mod 10.
I find summing mod 10 usually is easier. For example
Your sum
10+11+14+18+4+13+8+28+13+7 = 126
can be more easily done mod 10.
0+1+4+8+4+3+8+8+3+7 = 6 mod(10)
Then 6+9 = 5 mod (10)
It saves a bit on the brain cells.
i could not follow your method. how did you get all the groupings to begin with and what do the black single numbers mean? obviously the green number sequences are related to the numbers 1 through 9 which may or may not go there but there didnt seem to be any line of reasoning i could follow as to why the specific green numbers were in the specific squares. i would really dig it if you could elaborate. thanx!!
the_deacon, this site is mainly focused on Killer Sudokus. All solving tips given here are for the Killer Puzzles – not for the “classic” sudokus. From your message I gather you’re not yet familiar with the Killers – and this is the best place to become a Killer fan! 🙂