Mensa Sudoku

One of our testers thinks this sudoku puzzle by Sumanta Mukherjee tests a lot of different aspects of "intelligence": numeracy, spacial awareness, logic. What do you think?
Try the puzzle here:
cracking-the-c...
Here is a version without any colouring in the grid:
cracking-the-c...
Rules:
Normal sudoku rules apply. In cages, digits must sum to the small clue given in the top left corner of the cage. Digits cannot repeat in a cage. Clues outside the grid give the sum of cells along the indicated diagonal. Inequality signs in the grid point to the lower of the two cells involved.
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▶ABOUT US◀
Hi! We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships. We're also "cryptic crossword" aficionados. Mark is the twelve-time winner of The Times championship and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.
Thank you for watching!
Simon and Mark

[@GhostBombGames]

The most mind boggling thing to me, more than Simon's prowess at figuring out complex sudoku logic, is how he can add so many numbers together in his head without second guessing himself or using a calculator.

[@ArgumentumAdHominem]

I was going to comment the same thing. I have a 1-liner python script to tell me what can and cannot be in each cage, because otherwise these puzzles take ages. I wonder whether he simply remembers all combinations of all cages the same way as we remember the multiplication table, or whether he really does math that fast in his head. Him stating that 2 can't be in a 27 cage was very fast.

[@AquaShibby3000]

"And, we're off! This one.. oh, no we can't do this one yet" The logic giveth and the logic taketh away.

[@thomasm123]

I saw one of your other "zero given digit sudoku" videos and decided to try doing this one even though I've never done ANYTHING like it before - I don't even know any particularly special techniques for normal sudoku. I spent.... a WHILE attempting this and had a lot of fun but got nowhere. A few minutes in to this video you were already doing things that would never have occurred to me. I'm glad I had a go at it but am also very happy to see you perform absolute sorcery in completing this. I can definitely see why people get into this sort of thing!

[@12tone]

Break-in is incredibly gnarly, but once I got that it all unwound beautifully. Chasing the 6789s around the grid was really satisfying.

[@flikkie72]

Absolutely agree!

[@patrickv.3979]

I'm just finding this, but I absolutely adore the fact that one of my favorite music theory channels also watche(s/d) Cracking the Cryptic!

[@KyleBaran90]

While he's probably doing the logic correctly, I wonder how many times Simon has just gone off on maths and solved puzzles in completely unintended ways

[@CrackingTheCryptic]

I suspect a lot. I hate watching my solves back during editing because I notice lots of stuff I could have done differently!

[@stevesebzda570]

@@CrackingTheCryptic lol Bless your little adding machine head, lol. I got 442 for all of the cages so that shows ya how well I add. Did the 5 lots of 25 (getting 125) then I saw 27 and 26 (so I mistakenly did two more lots of 25 ). Now I see I was thinking the average of 24 and 26 for two more lots of 25 now. But I must have counted a couple twice anyway. Shows ya how well I add though lol. You do great (I count on you for that) . ;)) [[Oh, pardon the pun, "Count", lol ]]

[@stevesebzda570]

@Kyle Baran (and Simon) now I got 356 instead of 355. Jeez I can't add, lol . ;))

[@SoiKi3n]

I'll say Simon got a tiny trauma after doing the recent Ahaupt and Phistomefel puzzles (with much narrower logic path) so I'll let him do the harder logic this time :)

[@stevesebzda570]

.

[@KyleBaran90]

Is anyone else upset it took Simon 30 minutes to fill in the solved inequality he found really early on?

[@jandirks1603]

literally i was just sitting infront of my computer partly angry because i couldn´t tell him this

[@magc_csgo7098]

17:12 He explains why R8C6 can't be a 2, but misses out that R8C5 therefore can't be a 5. If he had just removed that pencilmark then, he wouldn't even noticed the 4-5 pairing at the end...

[@railgeekusa]

Yes, I was literally screaming at my television "SIMON 4 and 5 IN THE 12 CAGE!"

[@Ferrastar]

Don’t forget the 1 in box two that was sitting in r3c6 for ages as well

[@ericveneto1593]

Stuff like that is what makes Simon VERY frustrating to watch.

[@kevsgrove8025]

I revisited this puzzle after solving it using Simon's break-in, and I had trouble re-conceiving how he found the first numbers. I thought I'd post my logic train here in case anyone else is also struggling. The colored tiles all sum up to 355, so the white tiles must sum to 50. The mini-diagonals in the corners sum to 32, so the big white diagonals plus the mini-diagonals must be equal to 82. This 82 figure double-counts the middle tile of each corner box. The least possible sum for all the 5 asterisk-shaped patterns is 75 (digits 1-5, 15 each). Therefore our 82-figure is either the 75 minimum plus 7 for the double-counted cells OR 76 plus 6 (the minimum 1+1+2+2) for the double counted cells. The 12-cages' necessity for 1 and 2 restricts the 9 mini-diagonal's options so that the 75+7 scenario is our only choice. This part is still quite hard for me to grasp, I was only able to accept it as fact after playing around with it. If anyone has something to add, especially to the last point, I'd appreciate it!

[@_J_A_G_]

Late to the game here, but let me add the part you missed for completeness. First color the "double counted" center cells of the corner boxes yellow, to make referring to them easier. > The 12-cages' necessity for 1 and 2 restricts the 9 mini-diagonal's options so that the 75+7 scenario is our only choice. The key to this is the labeled mini-diagonal (called "little killer") in box 9. Only 1+2+4 can sum 7, but the center cell can't be 4 when the yellow sums to either 6 or 7. (If it is 4 it leaves 1 in each of the other three yellow squares, which clashes by soduku rules.) Now this 1-2 cell creates a virtual pair with the mandatory 1-2 in the 14-cage of box 8 (a 1 in R8C8 places the 1 in R9C5 and a 2 somewhere in row 8 box 8, same logic for 2 vs 1), which excludes both 1 and 2 from elsewhere in the row 8, specifically yellow cell R8C2. Knowing a yellow cell can't reach 4 (as before), this leaves only 3. Finally placing the first digit, a yellow 3 also rules out the yellow cells being 1+1+2+2=6. Even with a 3 in there, 1+1+1+3=6 and 1+1+3+3=8 is clearly not working either, so 1+1+2+3=7 is the only option. A 1 in R2C8 prevents placing the second 1 on yellow, so it must be the 2 and the yellow cells are fixed. He mentions this at 12:40, or rather 14:40, but written down it's more clear. There's another 10 min of logics left after that, but no major problems.

[@stephenbeck7222]

The break in is typically excellent form by Simon. From that point there are lots of solution paths, which, as is typical, Simon takes some of the most roundabout ones!

[@shennyboy212]

I love the way you explain everything to a novice level. makes these videos so much more accessable. love the vids keep it up

[@Kimakae]

I love seeing your smile when you find some logic! Thanks for sharing another awesome puzzle!

[@johnjdumas]

For some reason the 4

[@HunterJE]

Especially because if in he'd removed the 5 pencil mark in the less-than square at the same time he'd removed the 2 from the greater-than square he'd have had it automatically...

[@vasilybulochkin4622]

right? it also bothers me that he very often would place a digit and completely forget about it next second and will not check column/row where he placed it

[@Ferrastar]

But then he uses it right at the end to finish of the 4/5 pairs around the grid.. surely it is expert level trolling

[@HunterJE]

@@Ferrastar At the very end it was definitely intentional as he wanted to let that be what resolved everything, but seemed like he honestly overlooked it up to that point (and I get it, when you're focusing on one part of the logic those kinds of afterthought "oops need to stick this in to make the puzzle not break" notations can be easy to miss)

[@seancannon2193]

@@HunterJE Almost every time he scanned he hovered his mouse over it. Also, scanning it each time he did I never saw anything it'd actually give him. He was knowingly waiting for the payoff, I'm almost certain.

[@bristolrovers27]

Only 30 minutes!!! We’ve been getting used to hour plus !!!

[@maxgoodman87]

Now I'm going to have to watch Disney movies instead of Cracking the Cryptic Movies! ;(

[@leeannadimoulas5163]

This was a great puzzle. I love these videos! You do a great job of explaining things. I so couldn't do these on my own, but I can check in whenever I goof something up and watch for a minute, and then i'm off again. It's wonderful. Thank you so much!

[@forestroads]

This is one of the most beautiful puzzles and paths to solve it I have ever seen! I was struggling a bit to break in, but once I got in it was flowing nicely and I didn't even need the corner markings like Simon did. Especially with such a beautiful puzzle, I feel that the corner markings make it visually less appealing to even outright ugly :D And I feel Simon forgot about some key logic that could have helped him to solve it faster (it certainly helped me!). He concluded that those 5 boxes all needed a cross of 1-5. So that means that in each of those, the others cells are 6, 7, 8 and 9. Once you put those in the centre of each of those cells, have a look at the red cages: they will all have a digit in the middle along the edge, and you just need to pick the right combination of 3 of those 4 to make the total. You can go around the grid and have them done in 1 go, because they all interact. Then you can tackle the blue cages, followed by the green ones. No need for corner notations at all ... All in all, I don't think he did enough justice to this brilliant puzzle. If it would have been by phistomefel, he would have raved about how logic and therefore beautiful the path would have been. I guess it's all in the eye of the beholder ...

[@WesleySpikes]

My favorite moment in solving this was around 21:33 in Simon's solve video -- the 1 in box 2 was placable (Sudoku + Inequality leaves only r4c6), and then placable in box 6 (26 cage, already having a 5, removes 1 as a possibility in r4c9). From there, 1 in box 5 is placable, and I'm left musing"well if that isn't useless as can be!". Was the setter messing with us for fun? :)

[@zanzaboonda]

To give everyone an idea of how fast his brain works, I tried to just fill out the puzzle as he went (not solve it, just copy what he was doing), and I could barely keep up with that. And that's also with him explaining things. Imagine him (or Mark) doing a speed solve.

[@maximilianmaier3950]

He's insanely brilliant. I just finished this one myself a minute ago. It's Monday morning now and I started on Friday night. Was able to fill in a few digits quite early, even faster than Simon, but then I got stuck and had to come back to it several times until I finally got the break through I was looking for. Another one I've tried was the one with the perfect square in the middle, knights move and only 4 digits. That one I found pretty straight forward and pretty easy, but even when I did it for the second time where I did not even have to think about how to approach it, I couldn't do it as fast as Simon did it the first time.

[@kelperdude]

Thank you for the colored cages option.

[@PixelPumpkin]

I like to stop the video after Simon's initial supermath and solve the sudoku, and then pretend that I'm ahead of him, when in reality it still takes me twice the time to solve the rest of the sudoku -_-

[@rreagan3]

@@PixelPumpkin i do the exact same thing

[@timdunkley9173]

It took me more than six hours to spot the break-in that Simon spotted inside ten minutes.

[@kr12a2y]

30:52 and if I hadn't watched a ton of these videos in the last few months I never break in. Thank you, Simon!

[@williamnathanael412]

He's not missing the inequality sign in row 8 from 22:05 until the end of the video. He's saving the best for the last.

[@obroni]

I was shouting "5 is bigger than 4!" for 10 minutes while watching this. I really need to get out of the house more often...

[@RichSmith77]

But how does he know leaving the 5 and removing a 2 produces a beautiful finish, but doing the reverse doesn't? At the point he removes the 2, using the inequality, he could just as easily have removed a 5 and left a 2, hoping for a 2,4 pair left at the end, to disambiguate a sequence of 2,4 pairs. But it turns out it wouldn't have worked out that way, because 2 is not one of the inequality pair in the actual solution, so you wouldn't end up with a 2,4 pair. I don't know. I'm probably rambling. But it seemed like some good fortune was involved in it ending the way it did, so aesthetically pleasing.

[@alienrenders]

41:36 is my time. I did the break in slightly differently. I noticed that the diagonals in each corner box opposite the little killer clues almost always had to be at least 9. That meant at least one had to be 8 and it just filled itself. In the 124 diagonal, the other two digits are 3 and 5. We can't go above 9 so the center cell is a 1.

[@Eric998765]

Could have finished off the 1s about ten minutes earlier but still a good solve. This type of video is my favorite, where it takes 15-20min to get started then the rest a relatively easy to finish.

[@hangugeohaksaeng]

"I'm having some pangs of anxiety on seeing these inequality signs after Ahupt's puzzle the other day." Hahaha! Awesome. You were a rock star solving that thing. Really enjoyed it.

[@JPgreekgaming]

Everytime he get's bamboozled by some prior shenanigans he develops ptsd going forward, lol... I love Simon :)

[@mud6675]

I wanted to call Simon and tell him that there was 4

[@Stephen-Fox]

Lovely puzzle, even if I either made a typo or sudoku error leaving me flailing, and a wonderful solution video confirming that my logic was correct even if my sudoku wasn't.

[@Coyotek4]

The storm that hit the eastern US took my power out for 18 hours, so I only saw this puzzle this morning. I took a shot but soon gave up. . On the second try, I was able to get there in 27:25. I'll take it. Nice puzzle!

[@Rifi77]

25:11 for me. Once you find out that 12345 have to go in the 'crosses', it becomes a relatively easy puzzle

[@yadiracamacho499]

Nice sudoku! The word Mensa have always make me chuckle, because in Spanish menso/mensa can mean stupid. I find it ironic

[@patrickelliott2169]

Actually, not "that" ironic. I have known some damn stupid people in Mensa, some of whom went on to have grand carriers writing utter nonsense about everything from science they didn't comprehend, to social issues they hadn't bothered to ask anyone involved about before pontificating on them (sadly, a common theme). If the Spanish meaning included the term "savant" it might be about right. They tend to be very, very, very good at a) puzzle solves, with clear rules, which they know, and practice, so know exactly how to apply (but which applies to nothing in the real world at all), and/or b) word based puzzles, which again, require an in depth, and fairly worthless, understanding of obscure word usage, rules, social ideals from the time the words came into being, etc., by which one can "solve" such puzzles, but which someone a mere single generation separated from them might fail at spectacularly, while never the less being measurably vastly smarter in all other respects. Membership in such was interesting to me, 30+ years ago, when I was mostly lacking in friends, thought I was smarter than everyone else, had mostly As, while taking advanced courses, and was, in reality, ignorant, clueless, naive, and actually lamented not having "other people" around whom I could practice fairly useless things, like Chess, with, so I could prove to myself that I was somehow smarter. Now... man, there are so many supposedly smart people, some of them with memberships, who are bloody idiots about everything outside knowing a lot of logic tricks, for solving even more useless puzzles - not because they want entertainment, but because they think its the sort of entertainment that "smart people should want to be doing." Me.. Heh, I will play through a puzzle game in a day or so, with a lot of complex stuff in it, then watch anime the rest of the week, or something else "dumb" and "unproductive", but.. all things considered, I place my odds of doing something great for the world a bit below some of their own, but my risk of arrogantly screwing things up worse, because I was "too smart" to bother to understand what the problem really was first, vastly lower, in any conceivable set of circumstances. Not to say all of them are like that. There are a lot of really good atheists, for example - they, usually, just refuse to belong to any of the "groups", due to all the idiots in them at this point. lol

[@honigschlecker1]

1:03:12 for me. And very happy about it. 😀 Used the same deductions as Simon for a pretty long time.

[@Scuuurbs]

Sumanta: 16 Cups of T! Me: Triforce Kaleidoscope!

[@alternativeglasto]

For those of us who use the description given above to try to solve before watching the video: PLEASE EDIT THE DESCRIPTION TO SAY THAT NUMBERS CANNOT REPEAT IN A CAGE!!!

[@GREENx309]

Actually, both description [video, text] say you can't repeat a number in a cage and in his explanation he says killer sudoku rules, meaning above. Also, unless clearly stated otherwise, when with cages, it's pretty safe to assume numbers cannot repeat.

[@mawillix2018]

@@GREENx309 The video description apparently didn't note this at the time the video was uploaded.

[@alternativeglasto]

@@GREENx309 It didn't say that before, and while I agree that generally number cannot repeat in a cage, without the word 'Killer'appearing in the description that can't be assumed.

[@annalisasteinnes]

I wish there were a breakdown of the the maths in written form. I get that the sum of the white squares (50) plus the little killers (32) equals 82, and that the minimum that they *could* add to is 75. And that the difference between the minimum and the actual sum is 7. But I don't get why that difference must be made up by the specific 4 squares in the middle of the corner boxes. It's an assumption I would make, but I can't figure out the logic behind it.

[@louisesuth8141]

colour the diagonals blue, and the little killers green. . . there will be 4 squares which could be blue and green, that means those 4 are both totals

[@adaracaligo1469]

amazing puzzle! really needed this, today was tough. I'm so thankful for you guys

[@glennmelven3414]

What do I think? I think I never would have been able to get that break in. Even as Simon showed it I still didn't get the importance of it.

[@brianmcadam443]

I've watched enough of Simon's (Little) Killer solves that I knew right off the bat where the break-in was going to be. Simon did the arithmetic faster than I did, but my first thought when I opened the puzzle was to add up all the cages to find out the value of all the white cells, because in this sort of puzzle it's almost always either a minimum or a maximum, once you figure out how all the other clues act as constraints.

[@57thorns]

@@brianmcadam443 At least most of those they show. But the problem I have with that is that it is a lot of work (and I am mathematically inclined, so it is just laziness on my part).

[@jonahcomstock3061]

At least I understood this break-in watching it. The break-in for "Cracking the Cryptic: The Movie" was so complicated that I didn't understand it any better after watching SImon do it than I did before. And @CrackingtheCryptic Simon is an excellent explainer.

[@Raven-Creations]

That was a beautiful puzzle, both visually and logically. My logic for the start was slightly different from Simon's. I noted that, e.g. the 7 arrow needed to be 124, so the other box diagonal's minimum was 135. Repeating for all corner boxes meant the minimum left one degree of freedom, which was resolved by noting the virtual 12 pair like Simon. From there, it was similar to Simon's, although I tried not to use the most inefficient logic 😜 I did use some logic that Simon didn't , e.g. the red Ts on the left both needed a 6, so this acted like an x-wing in ruling out 6 from all other cells in columns 1 and 2. This was useful all round the grid, lots of times.

[@adrianhead6272]

Oh, how lovely and symmtrical... finished in exactly 24m24s, and the last two digits I entered were a 2 and a 4.

[@nadeemhajiiqbal9214]

Anyone else notice how after the initial break, the puzzle is simply figuring out which combination of 6789 go into each T? Each of them pretty much has a digit in them and the remainder is always somewhere between 21(678), 22 (679), 23 (689) or 24(789)!

[@billionai4871]

First of all, I love your videos and can't wait to finish this one. But second: DO you know Hexcells? It's a game that combines sudoku with minesweeper into brilliant puzzles, all hand crafted and super cool to solve. You will probably enjoy it a lot

[@VGInterviews]

a Simon puzzle that is under 45 minutes and the rules (almost) fit on a tweet? something is weird here

[@charlottestang9462]

16 cups of tea?! 9 seconds in and I'm already sold

[@keskinyavuz]

finding 3 is just brutal (I had to consult to Simon) and that's the whole point of this puzzle as the rest is easy.

[@ellaenchanted2399]

For corner pencil marks that are covered by a number, why not write a throwaway, no it's wrong number first? That way, you'd be able to see all the corner numbers.

[@kamirostorino9416]

it took me 30 minutes and 4 seconds… I can feel my brain sending signals in a way i'm not used to. Weird thing is… if I try to think Logically i freeze on one aspect fot too long… and when i don't try to think everything falls into it's rightful place

[@RoderickEtheria]

I calculated the cage totals, then immediately took each of the little killers and subtracted each of them from 15, adding 1 to each total. I then added the total of the four calculations to 15 as the minimum of the middle box empty squares, which told me I had 3 degrees of freedom.

[@RichSmith77]

You're probably aware, but since you didn't state it: That would require four 1s to be placed in the cross intersections in the four corner boxes, which breaks the Sudoku grid by having more than one 1 per column/row. You lose two of your degrees of freedom when you increase two of these intersections to be a pair of 2s.

[@RoderickEtheria]

@@RichSmith77 yes, I am aware. Wasn't part of my original calculation, but after a brief pause I was aware of it. The fact that two 12s with only one outlying cell each and two cells which we know are 1, 2, or 3 and cannot both be 3 look at the central cell of Box 7 also makes Box 7's central square impossible to be anything smaller than a 3, which breaks down the rest of the degrees of freedom.

[@victormanjarinsala2253]

Got to the 82 total and the difference of 7... Then forgot I was double-counting the central cells in each box U.U bad way to get stuck. Anyway, very nice puzzle!

[@Mephistahpheles]

Slightly easier way of doing it without double counting them. Once you have the 405 - 355 = 50, work on each corner box: 15 (diagonal minimum) minus little killer clue + 1 (center square minimum) = minimum for the white squares (7, 8, 8, 9) + 15 (box 5) = 47 + 2 (can't have 4 center 1's) = 49 Thus: one degree of freedom.

[@davecoleman1265]

Simon's great at explaining these, of course. But for these puzzles with a great deal of arithmetic it would really, really make it easier to follow if he had a scratchpad in his arsenal upon which to jot down notes that we could see. I don't know how it would work within the physical bounds of the video, but so often the challenge here becomes keeping an arbitrarily large set of numbers in your head all at once when there's no reason to not just write the things down. Easy for Simon and Mark, perhaps, but a considerable challenge for some of us.

[@serebix3685]

Simon says so many times "you probably shouting at the screen right now". And now was the first time this is true :D

[@zkhydro4985]

28:57 i haven't been watching intently but once i clicked on it to look i noticed the 12 cage in box 8. I guess 5 is smaller then 4 because that clue is too tough to figure out right away. Lol just jocking your strap.

[@zkhydro4985]

30:16 clicks on it makes a point on it still doesn't see that a 5 is smaller than a 4.

[@srwapo]

I needed help with the first part, didn't see how to get anything useful out of the negative space. The rest wasn't too bad after that.

[@KveruLars]

I've spent an hour trying to place anything but the 124 triple along the little killer 7, and failed. This is way too complicated.

[@HalfBakedLunatic]

That 45 inequality was sitting there forever ... was Simon just teasing us and keeping it to the end, since he knew it would disambiguate them for a more dramatic finish? :-)

[@danniild]

I found a second solution to this puzzle. r1c2, r1c4, r3c2, r3c4 are two 6s and two 7s, which could be swapped without affecting the rest of the puzzle.

[@ubison]

I used that 4

[@Mephistahpheles]

From the start: 123 can't go into ANY of the corners diagonals, 'cuz then you couldn't make any of the little killers. e.g. Box 7: Corners + center = 15 minus little killer 9 = 6. So the other two cells on the diagonal are at least 6 (white's at least 7). So 3 corner whites minimum 7, 8, 8, 9 + 15 for the box 5. That brings white square total up to a minimum of 47. But can't have 1's in all 4 corners (just 2). That brings white square total up to a minimum of 49....of the 50 possible.

[@MisterNohbdy]

The rules in the video say that digits can't repeat in a cage, but the description beneath the video doesn't. I presume the former is correct, as per typical Killer Sudoku rules? (Trying to avoid watching the video to find out, until I've done the solve.)

[@hai-mel6815]

Yes

[@mvm001]

Yes typical killer sudoku rules

[@dastr9596]

I opened this puzzle earlier today, sat down for 90 minutes and didn't find a single digit. I need to start with an easier puzzle if I want to start this kind of stuff haha.

[@TimwiTerby]

Throughout almost the entire video starting from 21:24, the 1 in column 5 could have resolved a fair bit. This may have been the longest I’ve seen you sit on something like that :)

[@neilramsey1368]

Another great puzzle

[@DOSSTONED]

I solved puzzle by trying and treat as normal killer sudoku, and took 31.98min. I believe my method is not a good approach so watched video again, Simon found the X and I even did not notice that! I know the huge gap to champions :)

[@SienAppelsien]

I tried this one but got stuck quite quick so i came to watch the video to help me on my way... The maths part with the crosses wouldve never occured to me

[@SondreGrneng]

If he resolves that 4/5 pair with the inequality via sudoku I'm gonna flip. All jokes aside, The logic required to even break into this puzzle boggles my mind. Edit: I'm cool with leaving it as long as you notice it's there, that's just the kind of weird I am.

[@flsal27]

18:08 why do we know at that point that the cells in the crosses add up to 15? I understand for the reasoning, to find the digits in the corner (1,1,2 and 3) but now the only thing that we know is that the white cells add up to 50?

[@magc_csgo7098]

1. The white cross has to add up to 50. (Whole grid (405) - Sum of all cages (355) = 50) 2. The 5 crosses in boxes 1, 3, 5, 7 and 9 could be anything, but the least they can be is 15 each, using 1,2,3,4 and 5 as the digits. (5 box-crosses × 15 = 75) 3. The 4 little killer clues together add up to ( 7 + 8 + 8 + 9 = ) 32. 4. If you add 32 to 75 you get 82, BUT we did count the center-cell of the crosses of boxes 1, 3, 7 and 9 all twice: Once in the white cross, and once in every little killer clue. 5. If we deduct the values of these cells and reduce it from 82, we cant go lower than 75 ( see my second point), so they can add up to a maximum of 7. 6. Simon deducts the values of these cells, and they add up tot the maximum they can be: (1 + 1 + 2 + 3 = ) 7. 7. Now he extracts 7 from 82 and gets 75: the absolute minimum you can make those cells add up to. Is it now clear?

[@samholden5758]

We know the crosses add to 50 + 8 + 8 + 9 + 7 - 1 - 3 - 2 -1 = 75. And thus much each be 15.

[@stephenbeck7222]

We know their minimum is 15, and once we determine the minimum of the 4 center cells is 7, that gives up all of the degrees of freedom available. It could have been that the center cells added to 6, and then one of the crosses could add to 16.

[@wanderlustwarrior]

55:31... but not honestly. I made some mistakes and had to double back, plus I wasn't certain how to start, and started with a different logic path, but got stuck and watched a bit for help.

[@DougCube]

@17:12 Simon removes 2 from r8c6 but kept the 5 in r8c5?? How strange.

[@satchan4401]

Well, he's a human too 🤷‍♀️

[@nicktecky55]

That Merlin is back! (6'50")

[@jasontedstone3926]

Great puzzle, first one I've done faster than you, Simon! So yeah, then I guess of course I would think it's great...

[@mud6675]

30:17 was my moment of relief!!

[@Croagge]

Not gonna lie, you saving that 5>4 inequality stressed me out

[@danielrhymer1762]

24:22 for me. Like killers so spotted the trick pretty quickly and it then flew out

[@Epicbird-hb5eg]

So has 2 a day become the norm, where a third is a bonus, I’m not complaining, I was just worrying about the thought of going back to 1 a day - a half dose

[@stephenbeck7222]

2 a day has been the norm since 75,000 subscribers! Unfortunately they have kind of plateaued at their subscribers and daily views is down from April and May significantly I think. Maybe 1 a day and give each of them some rest days during the week will help their form a bit? Can’t complain about the quality of the puzzles they choose to solve, that’s for sure.

[@Nevir202]

What was the point of the higher up inequality sign? He never used it... 🤔

[@isting4741]

He used it for eliminating 1 from r3c4. I haven't done that in my solve earlier and in the end, I had a "deadly pattern" that is resolved by this inequality sign.

[@Nevir202]

Nikita Voloshin ah, thanks, I remember that now that you mention it. 😊

[@jacobcombs1106]

Took me just short of 67 minutes. The initial part where he mathed out the white squares took me roughly 20 minutes longer than it took him lol. Then the rest of the puzzle took me another 10 minutes longer than it took him.

[@wobdoc]

Double 3 in the corner 👍

[@livedandletdie]

It was pretty easy after figuring out the cross at first. After that it was just fill in the numbers as they come. Man does Sumanta set really good puzzles, this almost felt like an Aad or Phistomefel puzzle, that it was very linear in it's solution. Yet still somewhat challenging. Although not the most challenging.. that goes to Ahaubt...

[@robertethanbowman]

Why can't the central X sum be 16 (1,2,3,4,6) instead of 15 (1,2,3,4,5) and have the four double counted be 6 (1,1,2,2) instead of 7 (1,1,2,3)?

[@RichSmith77]

Rewatch the video from 15:00 and Simon explains why r8c2 cannot be 1 or 2, so it has to be a 3. (Edit: fixed cell ref. Damn auto-correct)

[@arcanmster]

I think this is the first time I broke in faster than Simon. But then, I wasn't explaining everything out loud. Finished in 23:39

[@squallerrleon]

Cool puzzle, but there's not much else once you place the first 3. No way I was going to figure out to do all that math on my own!

[@thesphnx6836]

At 14:20 I legit thought the airplane was a Tardis noise

[@balkthor]

I don't like feeling dumb when doing sudoku's. But, to be fair, I think all of us are when juxtaposed with Simon and Mark.

[@EsperPinion]

I still don't get the logic of cells that add to 50 crosses are (1+2+3+4+5)*5=75 killer clues are 8+8+9+7=32 but then what?

[@EsperPinion]

nvm got it white cells = crosses - killer clues + corner centers 50 = 75 - 32 + x x = 7 1 1 2 2 is the minimum, which gives us 1 degree of freedom

[@mystreriousuploader]

3:30 RULES

[@TheFreeBro]

Hey I don’t know if you’ll see this but tomorrow when you stream obra dinn could you shout-out a happy birthday Tom. Don’t worry if you can’t.

[@BryanLeeWilliams]

Ok. I spent too much time trying this one. I do know that the white cells are 3 above the minimum. All values are minimum with 3 degrees of freedom. EDIT when Simon first adds up the values of the white cells he's forgetting that the little killer clues mean he can't make any of the corner cells 1,2, and 3. They are a minimum of 9 in one of the 8's,8 in the other 8, 8 in the 7, and 7 in the 9. 9+8+8+7+15 Total of 52. Hence the 3 degrees of freedom. EDIT Oh wow. I didn't catch that the 5 X shapes only had 1 degree of freedom. I wonder if I could do the puzzle knowing that. I'll never know because I'm not going to try. EDIT @ 19:43 No! Simon. Finish off the pencil marks in the corner. Please! @22:22. No! Simon. You have an inequality in the 12 cage. You can place the 4 and 5 and do more in box 5.

[@ericveneto1593]

The blue inequality was available for about 10 minutes!

[@buzzly108]

Let's get cracking: 4:36

[@PUBLICnoose]

Spent 80 minutes on this then made a mistake somewhere back spaced and couldn't find where i went wrong. Just going to watch simon

[@Crumbling_Vortex]

When it's halfway through the video and he hasn't even put down one number yet...

[@arturslunga3415]

Inequality restriction in box 8: Am I a joke to you?

[@Ayelis]

My score was 21:30 (as in, that's how far into this video I had to watch before I could figure out how to solve it myself, I was clueless before that) xD

[@stevelwall99]

After a certain point this puzzle practically solves itself! Quite elegant.

[@Max16hr]

Solved in 3:22:23 🙂

[@Jim_Fries]

This made my brain hurt. In a oddly pleasant way.

[@randysavage1011]

Can you please narrate my life?

[@kaushalagrawal6258]

done in 1:40:00

[@cyclopsboi]

i was screaming about that inequality sign for so long and he waited until the end to unroll it :/

[@DrNoBrazil]

bday boy!

[@ariondys]

suspicious you knew what to do to get started...

[@RichSmith77]

Yeah, I'm beginning to suspect he's quite clever and a very experienced puzzle solver too.

[@victorolosaurus]

I don't like this style of puzzle, that has a really steep gradient in difficulty. I had nothing, used simon's help to start and than it was really easy

[@donnathelightningbug]

The upper inequality wasn't even necessary for the solve!

[@RichSmith77]

Used at 21:25 to eliminate 1 as a candidate for r3c4.