The last two years it has been far easier for me to do KSs than when I first started. For me, lots of practice has made a difference. I know you have done all the books, but for others, solving the two KS books makes a difference in your ability do to the puzzles.

Like you, I sorted out columns on the right hand side.

After eliminating as many possibilities as I could analytically, I noticed that cells C4, D1, and F7 were affected each other, and only had two possibilities. That was where I started with trial & error.

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Not wanting to include spoilers for those who haven’t done it yet, I will say that I managed to sort out a few of the cells in the 3 columns on the right hand side of the puzzle and this gave me the start I needed to work through it.

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pnm wrote:

The Friday Killer Sudoku is supposed to be the most difficult one of the week,

but yes, yesterday's does seem a step up than what is usual on a Friday

I’m surprised to see that it’s already been solved 240 times, which is not that far off the average number of solvers over the previous 4 Fridays. I must have some kind of a blind spot, but hopefully I’ll manage to get my head around it.

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I’d welcome any insights from those of you who’ve solved it. How did you approach the puzzle and how did you get your hooks into it? I find I tend to struggle with Killer sudokus far more than I do with other puzzles and I’m struggling to understand why this is the case. Any insights anyone can provide would be extremely welcome and very much appreciated.

Thanks

Paul

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Rectangles can be 3x3, 3x6, nx9.

Here's a list of useful relations used solving the puzzle:

C1 + C2 + A3 + C3 = 22

D1 + A4 + C4 + D4 = 15

D1 + F1 + E3 + F3 = 20

G1 + I2 + H3 + I3 = 14

F1 + I4 + H4 = 13

A4 + C4 + A6 + C6 = 21

A3 + C3 + D4 + A7 + C7 = 22

G4 + H4 + I4 + G6 + I6 = 24

A7 + C7 + C8 + C9 = 23

A6 + C6 + D8 + D9 = 17

D7 + F7 + D8 + F8 + D9 + F9 = 27

G7 + I7 + G8 = 12

I6 + F8 + F9 = 13

D1 + D4 + A7 + C7 = 13

C5 = 1

D1 + D4 + D8 + D9 = 11

F2 + F3 = 5

I1 + I5 + I8 + I9 = 23

B4 + A5 + B5 + B6 = 23

B4 + A5 + B5 + B6 = 23

F2 + F3 = 5

I1 + I5 + I8 + I9 = 23

G5 + G9 = 15

B2 + D2 + G2 + I2 = 25

B7 + E7 + G7 + H7 = 21

For example C5=1 is based on cols A,B. The cages of this region total 91 and C5 is the only external point.

F2 + F3 = 5 is similarly based on the region consisting of columns A-E.

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paulv66 wrote:

It was definitely quite tricky. I managed to fill in or have pencil marks in columns G to I, but it was difficult to get a hook into the other 6 columns. I decided to run with one of two options for a particular cell and luckily, this proved to be the correct option and I managed to complete it on Friday.

But I note that it has only been solved 138 times, compared to an average of over 280 times for the preceding four weeks. So it definitely caused a lot of people a lot of problems.

Exactly Paul. Columns G to I were filled at first. Then... almost no clues!

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But I note that it has only been solved 138 times, compared to an average of over 280 times for the preceding four weeks. So it definitely caused a lot of people a lot of problems.

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At a certain point, no strategy at all and a lot of possible paths in front of me, so many to discourage trial and error attempts...

Did anybody feel my own impression?

Usually, I trust a lot in the difficulty rate, but this time it wasn't so high (147.1), nevertheless the solving has been very tough...

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(at https://www.amazon.com/gp/product/1517766028)

For some reason the book description was missing from the page, for example (!)

I also updated the cover image (darker background, different font, higher contrast)

I'm looking to add endorsements for this one too (similar to the one that's now on the BBE page,

i.e. "I love these puzzles, they keep my brain alert, which helps a lot when teaching math!", J. Bloemhof, high school math teacher),

so if anyone is up for this, let me know

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Friday's difficult Killer sudoku rated 183.1

The puzzle shown above rated 15.8

Based on my method that makes this puzzle look very easy, as I had said before. I thought it might be of some interest to compare it to a difficult puzzle.

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