Sudoku Puzzles #137, #138, #139, & #140

By: Dan LeKander

Volume 18, Issue 2, February 2023

Forrest Gump might say, “Sudoku is like a box of chocolates; you never know what you’re going to get”.

Please enjoy the puzzles for this month.

Please let the author and this editor know how you managed.


We start with a Sudoku puzzle in progress, where it appears that there are no more obvious or not-so-obvious clues.  Can you find the hidden clue in Puzzle #137?


(The answer follows the conclusion of Puzzle #140, the feature puzzle for this month)

Logic Puzzle

Difficult rating … 7/10
(Rating based on puzzles not requiring advanced techniques)

Puzzle #138

Impossible to solve?

Impossible?  No.  Difficult?  Extremely.  

Puzzle #139 should be challenge for you.  Advanced Techniques (Steps 6 and/or 7) are required.  Difficult rating 9.8/10.

Puzzle #139

Feature Puzzle

Difficult rating …  3/10
(Rating based on puzzles requiring advanced techniques)

Puzzle #140


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


The first thing we observe is that C4R7=7.  C8R5=8.  C6R8=9.  C5R7, C5R8 & C5R9 are limited to options 1, 4 & 8.  This leaves C5R1, C5R3, C5R4 & C5R5 with options 2, 3, 5 & 6.

In box six a 4 can only exist as an option in C8R6 and C9R6; therefore, a 4 cannot exist as an op-tion in C1R6, C3R6, C4R6 and C6R6.

In box six a 7 can only exist as an option in C7R4 and C7R5; therefore, a 7 cannot exist as an op-tion in C7R1 and C7R3.

In column two the options 2 and 3 can only exist as options in C2R5 and C2R7.

Now your grid should look like Example #140.1 below:

Example #140.1

This completes Puzzle Preparation Steps 1-4.  Normally, next we would fill in options for all of the unsolved cells.  However, there are two options that would make excellent candidates for Step 6 exercises.

As in previous articles, we determined a particular number was a potential for a 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 do you see that are good candidates?   Yes, the 2’s & 3’s.  We do not need the options of the unsolved cells to be listed in order to con-duct these exercises.

If one or both of these exercises is successful, we could save quite a bit of time not having to fill in the options for all unsolved cells and potentially shortening the time to solve the puzzle.

We will start with the 2’s and perform a Step 6 exercise, Dan’s Yes-No Challenge”, per Example #140.2 below, using C2R5 & C2R7 as our starter cells highlighted in yellow.

Example #140.2

Either C2R5 or C2R7 has to be a 2.   First, we will assume C2R5=2 and mark it with a capital Y, for yes.  Then we will mark the cells it affects with a Y or N, indicating a yes or no.

Next, we will assume C9R1=5, and mark it with a “y”.  Then we will mark the cells it affects with a y or n.

We see that C8R7 & C3R8 are marked N,n.  It means that these cells cannot be a 2, regardless of which starter cell is a 2.  The 2 can be eliminated as an option for those cells.

Now, in Example #140.3 below we will conduct the same exercise with the 3’s with the same starting cells.

Example #140.3

We see that C7R3 & C9R7 are marked N,n.  It means that these cells cannot be a 3, regardless of which starter cell is a 3.  The 3 can be eliminated as an option for those cells.  We also see that C7R8 is marked with a Y,y, meaning that cell is a 3 regardless of which starting cell is a 3; there-fore, C7R8=3.

Now our grid should look like Example #140.4 below:

Example #140.4

In box nine a 2 can now only exist as an option in C8R7 and C8R8; therefore, a 2 cannot exist as an option in C8R1, C8R2 and C8R3.

This leaves C7R1 as the only unsolved cell in box three that can be a 2.  C7R1=2.  Then, C6R2=2.  C5R5=2.  C3R6=2.  C2R7=2.  C8R8=2.  C3R7=3.  C2R5=3.  C4R6=3.  C5R3=3.  C9R2=3.  C6R3=6.  C8R2=6, and so forth, leading us to an easy conclusion, as per Example # 140.5 below.

Example #140.5

This feature puzzle is an example of being solved by just two Step 6 exercise, and we did not even have to fill in the options for the unsolved cells.  This clearly illustrates the power of a successful Step 6.

May the gentle winds of Sudoku be at your back.

By Dan LeKander

Clue for Puzzle #137 …  did you find the clue?  If not, read on.
Check row 3.  What do you see?

We see that C6R3 & C7R3 are the only two cells in row 3 that can have options 4 & 9.  Now, the only unsolved cell in row 3 that can be a 5 is C5R3.  C5R3=5.  This puzzle will be interesting to complete, requiring advanced techniques.  Difficult rating = 7/10.

Editor's Note: Hard to believe we are into 2023 and that our friend Dan LeKander has provided 4 more puzzles.  Looks like he will do so in the coming months, so your challenge Sudokus are alive and well.

Recently someone wrote to ask how to fill them out online. Unfortunately, you need to print them yourself,  but that is easy to do and I know you will have just as much fun.

And, 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 by contacting

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, November 2021, December 2021, January 2022, February 2022, March 2022, April 2022 , May 2022, June 2022, July 2022 , August 2022, September 2022, October 2022, November 2022, December 2022, and January 2023

Posted in: Volume 18, Issue 2, February 2023, Sports

Please click here if you are unable to post your comment.

Submit an Article

Do you have an article you would like to submit? Click here to participate.