Sudoku Puzzle #96 & #97

Clueless?

Puzzle #96

As a bonus each month we start with a Sudoku puzzle in progress, where it appears there are no more obvious or not-so-obvious clues.  Can you find the missing clue in Puzzle #96?

(The answer follows after the conclusion of Puzzle #97, the feature puzzle for December)

Feature Puzzle

This “impossible” puzzle #97 below reinforces the concept presented last month for solving Step 6 exercises without filling in the options for the unsolved cells.  If you did not read that article, please click on and read the November 2021 article.

Puzzle #97

DAN’S 8-STEP APPROACH TO SOLVING ALL SUDOKU PUZZLES

Once you have  completed the puzzle, to the extent that you have filled-in all obvious  answers and have written all potential options across the top of the unsolved cells (PUZZLE PREPARATION), Dan recommends the following Steps to complete the puzzle.

Step 1:  Sudoku Pairs, Triplets and Quads – See September 2015
Step 2:  Turbos & Interaction – See October 2015
Step 3:  Sudoku Gordonian Rectangles and Polygons – See November 2015
Step 4:  XY-Wings & XYZ Wings – See December 2015
Step 5:  X-Wings – See January 2016

Step 6:  DAN’S YES/NO CHALLENGE
Step 7:  DAN’S CLOSE RELATIONSHIP CHALLENGE
Step 8:  AN EXPANSION OF STEP 7Steps  1-5 are relatively common techniques and are explained in the TI LIFE  articles above. Steps 6-8 are covered in detail, in Dan’s book.


PUZZLE PREPARATION

Prior to utilizing Steps 1-8, complete the 5 Steps of Puzzle Preparation …

  1. FILL IN DATA FROM OBSERVATIONS
  2. FILL IN OBVIOUS ANSWERS
  3. FILL IN NOT-SO-OBVIOUS ANSWERS
  4. MARK UNSOLVED CELLS WITH OPTIONS THAT CANNOT EXIST IN THOSE CELLS
  5. FILL IN THE OPTIONS FOR THE UNSOLVED CELLS
    We will complete all of the first 4 steps in the order we observe them, until we conclude all Puzzle Preparation Step 1-4 clues.

The first thing we observe is that C4R5=1.  C6R4=5.  C1R8 & C2R8 have options 12.  C5R4, C5R5 & C5R6 have options 267.   These clues give us Example #97.1 below:

Example #97.1


So now, before we complete step 5 by filling in the options for all the unsolved cells, we will look at the puzzle and ask if there are any good Step 6 potentials.  As in previous articles, we determined a particular number was a potentially successful Step 6 exercise if that number appears as a given answer in 3 separate boxes, such that the boxes are not side-by-side, nor over each other.  Which numbers are good candidates?   Yes, 3 and 9.

We will first pick the number 3 and perform the exercise.  At this point at your home, you would put green tokens on two starter cells that are 3’s and black tokens on all unsolved cells that could have the option 3.  For purposed of illustration, in Example #97.2 below we will highlight two starter cells in green, and the unsolved cells that could be a 3 in yellow (vs black).

Example #97.2

Now we will perform the exercise.  

We will use C3R2 and C3R5 as our starter cells.  We will start with C3R2 and assume it is the 3.  Then we can see that C4R2 & C5R2 cannot be a 3, then C4R1=3, C4R8 & C4R9 cannot be a 3, then C5R8=3, C9R8 cannot be a 3, C8R9=3, and C8R5  cannot be a 3.

Next, we assume that C3R5 is the 3.  It follows that C8R5 & C9R5 cannot be a 3, then C9R4=3, then C9R8 cannot be a 3, then C8R9=3, then C4R9 cannot be a 3.  So regardless of which starter cell is a 3, C4R9, C8R5 & C9R8 cannot be a 3, and regardless of which starter cell is a 3, C8R9=3.  

It follows that a 9 can only exist as an option in C7R8 or C7R9, so, C7R4, C7R5 & C7R6 cannot be a 9; therefore, C8R5=9.  The 9’s are quickly dispatched, and then the 3’s, leading to an easy conclusion per Example #97.3 below …

Example #97.3

May the gentle winds of Sudoku be at your back.

Dan LeKander


Clue for Puzzle #96 …  did you find the clue?  If not, read on.
Let’s look at row 8.  We see that C1R8 cannot have options 7 or 8, and neither can C5R8 or C8R8.  This leaves the two unsolved cells C3R8 & C4R8 as the only two unsolved cells that can have options 78.  We know that C1R2=4; therefore, the only cell in row 8 that can now be a 4 is C5R8.  C5R8=4.


Editor's Note:  December 2021!

Dan's fishing season has moved to the sunny south, but you can see from Puzzles #96 & #97 he is still creating puzzles for TI Life readers.  Thanks Dan and your wonderful  proofreader (and, as they say, better half) Peggy, once again you have given us a nice challenge.

It was back in January 2016, when we published a final article in Dan's Series of Steps to learn the logic of Sudoku –  he asked if we would like a puzzle to solve every month  . . . this editor said an enthusiastic - Yes, please!

If you have not already done so, I suggest you purchase Dan’s book: “3 Advanced Sudoku Techniques, That Will Change Your Game Forever!” Purchase of a book includes a 50-page blank grid pad, 33 black and two green tokens. The book is available online at ebay.com.

Be sure to read the TI Life's review of Dan's book by Jesse Kahn published in Jun 2015.

Here are links to all past Sudoku Puzzle Challenge beginning: February 2016, March 2016, April 2016, May 2016, June 2016, July 2016, August 2016, September 2016, October 2016, November 2016, December 2016, January 2017, February 2017, March 2017, April 2017, May 2017, June 2017, July 2017, August 2017, September 2017, October 2017, November 2017, December 2017, January 2018, February 2018, March 2018, April 2018, May 2018, June 2018, July 2018, August 2018, September 2018, October 2018, November 2018, December 2018, January 2019, February 2019, March 2019, April 2019, May 2019, June 2019, July 2019, August 2019, September 2019, October 2019, November 2019, December 2019, January 2020, February 2020, April 2020, May 2020,  June 2020 and July 2020, August 2020,  September 2020, October 2020, November 2020 and December 2020, January 2021, February 2021, March 2021, April 2021, May 2021, June 2021, July 2021 , August 2021, September 2021 ,  October 2021 and November 2021.

(Each month we suggest you go back, say October 2016, and see if you can solve the puzzle easily - and PLEASE let us know.  This editor went back . . . and Wow that was fun.)