Internet shocked by teacher's mistake

[@Haus_360]

Ugh, I always hate it when I have to wait 5 minutes so my board is in 1 piece

[@milanfanas]

Yeah, it is annoying indeed. In the morning I have to wait 40 minutes for my table to be in a single piece before I can have breakfast

[@zombination1543]

Lol

[@zedlol5679]

ONE PIECE

[@zombination1543]

@@Haus_360 yesterday, my desk was extra hard, and it took me a whole hour to cut it into one whole piece. Ugh, so annoying!

[@rodrigoqteixeira]

Damn, and when I wait 0 minutes and it goes to limbo

[@dhy5342]

The teacher was counting pieces, the student correctly counted cuts.

[@yackawaytube]

You are right.

[@Ps119]

yup, you got it in a nutshell

[@wiseacredave]

I agree. This is not an "off by one error". It's an error in using the wrong unit rate.

[@AlexanderOsias]

Precisely.

[@DataUser1357421En]

Yes Makes me think perhaps you could also count jobs - Marie can be working just as fast per job, so 10 mins for the other one too

[@mhoover]

I was a software engineer for 20 years, 19 of which were spent correcting off-by-one errors 😂

[@bigolbearthejammydodger6527]

I know right - If an off by one error is acceptable to a maths teacher or in presh's case professor... damn home schooling looking like a good choice! (also a life long code monkey)

[@ProuvaireJean]

Are you sure it wasn't 20?

[@igrim4777]

So you were a software engineer for 19 years, 20 of which were spent making off by one errors?

[@mhoover]

@@igrim4777 Come to think of it...hmm... let's see...

[@DerMarkus1982]

That's not off-by-one. That's a stops-vs-stretches problem. "fence-post error" might be more appropriate although "off-by-one" is a fencepost type scenario. Not all fruit are apples, though.

[@blacklight683]

Poor teacher, didnt know that you get 1 free piece at the start

[@ayhanrashidi1563]

ONE PIECE!??!??!

[@WillKester]

@@ayhanrashidi1563 THE ONE PIECE IS REAL!!!!!!

[@odio_stationofficial3420]

yes, ​@@ayhanrashidi1563 ONE PIECE!!!

[@joshuabergman3292]

​@@ayhanrashidi1563it was always real!

[@ElderonAnalas]

meanwhile me out here thinking "10 mins to get 2 pieces, 20 mins to get three, and a spare one" because you're cutting two different boards.

[@luke34994]

That must be one really dense board for it to take 10 minutes to saw it into 2 pieces

[@perrygershin3946]

They forgot to say the board was 18 inches wide and 4 inches thick.

[@greenman1411]

Dense board and an even denser teacher!

[@tillianator5931]

or marie is shockingly terrible at using a saw

[@Gordon_L]

The teacher was told to use a hand saw and she thought that's what a hacksaw was ... 24 tooth blade at that.

[@thornhillplumbing]

Try cutting a sheet of plywood/OSB/MDF (or any other wooden board) in half with a hand saw and see how long it takes.

[@jmcdermid]

WRONG WRONG WRONG Marie is ambidextrous, so with a saw in each hand, it only takes her 10 minutes to cut the board into 3 pieces.

[@fgvcosmic6752]

Nah but it does say that they work just as fast, and using 2 hands is working twice as fast

[@reedplaysgames]

Taking into account strength imbalances and bilateral deficit tho it should actually be closer to 15ish lol

[@cocobeans3742]

⁠@@fgvcosmic6752yeah but you can argue the hands are working just as fast, no one said how many hands were working.

[@ironfistgaming8945]

Yayyyyyyy🎉🎉🎉🎉🎉

[@danmessi8142]

Wrong, it never said she was sawing off the board into equal pieces, after making the first cut in 10 minutes she gives up and just cuts the corner of the board making it only around 11 minutes to cut it into 3 pieces.

[@AzureKyle]

Basically, it's a case of misidentifying the x in an algebraic equation. The teacher defined x as the number of pieces, when x is actually the number of cuts. So she started with 2x=10, when it was really x=10. This is a common problem with word problems, where people pay more attention to the numbers than the actual word problem itself.

[@lanarkorras4411]

Yep. That's the crucial idea to keep in mind here.

[@lexlancelian8481]

well, you can use X as teacher used too, but he never realized that she STARTS with one piece (ONE PIECE IS REAL)

[@darnoc0010]

It's called critical thinking and many people never learn it.

[@redstonewarrior0152]

It's kinda like those tests where you are told to follow the directions at the top of the worksheet and most people will just ignore the instructions and begin answering all the questions on the worksheet when the directions just say to write your name at the top of the page, answer quedtion 15, and then turn in the worksheet.

[@AzureKyle]

@@redstonewarrior0152 Especially when some of the directions say flap your arms like a bird or other silly stuff.

[@emeraldaly7646]

This is like that old riddle "If you're running in a race and pass the person in third place, which place are you now in?"

[@igrim4777]

Indeterminate. On a circuit race the persons in first and second places could each pass the person in third place without changing race order.

[@fgvcosmic6752]

​@@igrim4777fine then. You're running on a straight track. Happy?

[@deept3215]

@@igrim4777 They wouldn't pass them, they would lap them them

[@davelordy]

It depends on which direction you're going 😁

[@isaiah0xA455]

@@deept3215 that’s a semantic argument, and a bad argument too. Lapping someone involves passing them *by definition*

[@RainbowGale]

0:45 My brain literally broke after I heard that explanation. I was just so flabbergasted by this “teachers“ reasoning that I just could not even. I say that teacher gets an F. Seriously.

[@UTU49]

I think the worst thing a person can do is be unwilling to double-check their own work. Particularly in Math. I had many Math instructors who were exemplary. Rather than being bitter at being corrected, they seemed to actually really appreciate it.

[@Dragon-Believer]

This is pretty typical. Smart kids don't want to be teachers because school is boring and mostly a waste of time. Average kids want to be teachers because school is interesting. Many classes have several kids who are significantly smarter than the teacher.

[@cosmicball1670]

that's literally how i solved it lmao

[@grimmspectrum1547]

Except for the fact in this case the teachers actually right 😂

[@天山]

@@grimmspectrum1547Have u tried thinking

[@AnnieTGM]

So it turns out that the shape of the wood board is ambiguous and the piece in the drawings was a lie.

[@AlexanderScott66]

It just wasnt to scale

[@piotrtoborek2442]

Nah it turns out some people tend to missinterpret questions by omitting some words used

[@gegor41311]

literally the funny cheese question

[@wessanders4566]

Dude! Check out the picture of the board that is being cut (next to the question). Nothing ambiguous.

[@AlexanderScott66]

@@wessanders4566 But it's "not to scale"

[@ciscou]

There are two difficult problems in computer science: naming things, cache invalidation, and off by one errors.

[@l.clevelandmajor9931]

And you just got one off!

[@ciscou]

@@l.clevelandmajor9931 that's the joke

[@bigolbearthejammydodger6527]

that is going in my memes channel for the work discord!

[@Aphelia.]

good one

[@verkuilb]

If there are two things I’m not good at, it’s counting.

[@sitnamkrad]

I would not be so kind to give the teacher a break. It's one thing to make an off-by-one error. But the teacher should have had access to the official answers. Especially since the concept of requiring only one cut to turn the board into 2 pieces is the heart of the question. But that's not the only reason. If this was the result of an actually graded test, that means that either not enough students gave the right answer to make the teacher question theirs, or the teacher simply refused to reflect on their own answer. Neither case reflects well on the teacher.

[@neh1234]

To be fair, I don't think any self respecting adult would feel the need to check on the official answers for such an elementary question.

[@Cau_No]

​@@neh1234and that's the reason why so many adults keep being posted on r/confidentialIncorrect.

[@Trozfol571]

​@@neh1234There's a difference between respect and arrogance, the only teachers who never check the official answers are arrogant stuck up teachers who believe that they're right over the students because of some teachers degree, even professional experienced teachers (were I'm from anyway) still check the the official answers and do research cause they have humility and don't close their minds to those they deem inferior to them. It doesn't matter if your older, wiser, smarter, more qualified or better overall than others you can still be wrong and/or misunderstand something as basic math.

[@alihms]

​@neh1234 Not doing any verification is the main reason why people get trapped with one-off error answer. As a teacher, it is her duty to be aware of this type of error.

[@frenchguy7518]

I would only give the teacher a break if they admitted their mistake when it was explained to them, and apologized to the student. Otherwise, they really have no business teaching anything to anyone.

[@Jerry_Fried]

I submit that there is no one anywhere who would consider a torus to be a “board.”

[@geraldgomes]

If the board was a square, then the teacher could be right. But the dimensions of the board were not specified and a board is usually not a square.

[@jeremyashford2145]

Submission refused. I would. I would, and do, call a piece of wood of any size a stick. A stick with a hole in it, be it a knot hole, or a worm hole, or a drilled hole, or whatever, is a torus.

[@weevilinabox]

Does this make it more acceptable? Starting with a square or rectangular board, cut a circle (or any other 2-d shape) from the middle of the board, resulting in two pieces with one cut. If the next cut is from an outer edge to the hole in the middle, then there are still only two pieces after the second cut. A third outer-to-centre cut will result in three pieces. Edit: extending this silliness, cutting _n_ non-intersecting shapes from the interior of board will yield _n+1_ pieces. It is then possible to make _n_ further cuts without creating any more pieces, by first cutting from an edge to an interior hole, then cutting from the first hole to the next, and so on. The _n+1_ th additional cut would be from the last hole to an outer edge and would finally generate the _n+2_ th piece. I'm thinking of the hole cuts as being in a row, but I wonder of there's a pattern of holes and joining cuts which breaks this pattern without allowing joining cuts to intersect each other.

[@nicholasreilly3218]

@@geraldgomes And the drawing in the margin depicting the board being cut is clearly not a square, so it is implied that the board is longer than wide, and is being cut at it's narrowest dimension

[@TheEudaemonicPlague]

@@jeremyashford2145 Jeremy, you need education...a torus is not just something with a hole in it. Look it up, learn something.

[@computermariobross]

Instead "It took Marie 10 minutes to saw a board 2 times. How long would it take her to sae another board 3 times?"

[@Bashaka104]

But she only sawed it 1 and then 2 times You are counting pieces

[@weirdbunmi]

​@@Bashaka104Yes. OP is saying if the teacher wanted to use the reasoning they wanted, where 2x=10 and 3x=15, they would need to reword the question like this.

[@Kalimangard]

I'm not sure which is more embarrassing for the teacher: Claiming that the time needed was a constant multiplied by the amount of pieces you get rather than the amount of cuts you make or the statement "10=2"

[@Benkinjo9419]

This teacher is a perfect example of someone who never understood and thought about topics, just learned them. He simply made the calculation with the time and wood pieces instead of time and the actual work done which is the amount of cuts. No critical thinking, just using the formula. When i was tutoring i always used sneaky questions like this. Makes the kids laugh, a bit angry sometimes, but in the end they not only improve in their classes but learn to think for themselves and ask critical questions. This is something that should be ruthlessly hammered in to ongoing teachers.

[@jbird4478]

I always gave snarky answers to those questions, because teaching math is not supposed to be about trick questions. So in this case I'd write: it depends on the size of the cuts, among other things, but the answer you'd want me to write is 15.

[@bigolbearthejammydodger6527]

As you are a maths teacher I shall re post my comment here for you. Its so Important to teach students when problems can be solved in different ways and when its appropriate to use certain methods. This simple maths questions is deceptive because using simple maths of ANY kind will result in an incorrect answer. As a senior person in industry I have to spend so much time UNTEACHING kids what they have learned incorrectly at school or university! You seem like one of the good ones though so I encourage you to give my analysis of this problem to the kids to mull over - show them that sometimes the obvious calculation problem is actually much more complex in the real world. my comment: This isn't just a MATH TEACHING fail, its a MATH fail. YOU ARE WRONG PRESH! - there is actually insufficient information to solve accurately. This is a systems analysis question - not a maths question - and it must be solved as such! Math with give you a WRONG answer! The job requires you to get a board from location 1(t1), get a saw from location 2(t2), travel to a work bench at location 3(t3) - then set up the work bench to do the cut(t4), then do the cut(t5), then put the tools away and deliver the cut wood (t6) Ie Total Time T = t1+ t2+ t3 + t4 + t5 + t6 whereas for problem 2 its: T = t1 + t2 + t3 + t4 + 2(t5)+Overheads + t6 so in reality its more likely to be about 11 minutes - depending on all the values. You are wrong, the student was wrong and the teacher was wrong - and my answer is only right if i have correctly assessed the problem - which given the lack of detail is unlikely. What you have really shown here is why we CANNOT use maths to solve most real world logistics issues. If we were to use maths to solve this question for a home depot or homebase shop where they cut wood to order it would result in incorrect assessment of the time and loss of money or safety fails.

[@Benkinjo9419]

I should clarify that I am not a real teacher as in teaching whole classes at school, I just tutored and helped kids struggling with their grades in a private institute while studying. Atm I work in accounting and also do a lot of work with new and young hires. Because of that I really loved your comment and especially your phrasing, I couldn't agree more. With this much experience and creative style of thinking I am sure there are a lot of young colleagues really appreciative of you. And I am also very glad for your comment because it called me out for being a fool as well. That "sneaky operating" I mentioned earlier includes deliberately taking a false stance in order to be called out as well. Discovering this kind of thinking for one self and teaching it to the younglings is one of the most important things I believe. Having 5-10 students gang up on you for being wrong, even though there are still another 2 or 3 different "right" answers in the room were always among my favourite moments. In the end the only right answer that everyone could agree on was, that there were no right or wrong answers to these questions, just different ways of thinking. That video reminded me of that and I couldn't resist to let my sneaky side out ^^ @jbird4478, students like you I always liked the most. Nothing better and faster than immediately getting a smug answer to your face when trying to form such a discussion. I hope that you got at least a few thumb ups or even high fives for your answers ^^

[@jeremypnet]

@@bigolbearthejammydodger6527lol. Not a maths question you say whilst using two mathematical formulas to demonstrate how to solve it. It is a maths question, but you have to know what model to apply. Also your model is wrong in different contexts. I’m standing here at my workbench with my saw in hand and my two boards with the places to cut already marked. I’m very untidy, so I never put my tools away and somebody else is waiting to deliver the wood.

[@1947dave]

@@bigolbearthejammydodger6527 The question is about the action of sawing a board, not obtaining a board and saw or doing any of the other preparatory work you have included. In short, you've made the mistake of not answering the question by overthinking it, perhaps deliberately lol. That's why many students fail to finish tests in the allotted time!

[@geoninja8971]

Wouldn't surprise me at all.... here in Australia we now have sports teachers teaching maths....

[@MindYourDecisions]

Was it due to budget cuts? But now that professional sports is run by analytics, maybe the sports teachers will be good math teachers ;)

[@Phymacss]

Physics for us😭😭 They bring us teachers who don’t know how to convert between gram and kilogram 💀💀💀

[@ObsidianParis]

Ironicaly enough, a sport teacher would probably have come to the correct solution from the beginning…

[@majinnemesis]

@@ObsidianParis a sport teacher would probably just get a piece of wood a saw and try it out in practice since sport teachers tend to be more physical and like to move

[@laars0001]

⁠@@MindYourDecisionsIn Gr 7 the gym teacher was also the math teacher AND the health teacher, when I was 12.

[@nix_]

Fam the way my brain cycled through both answers is something else. 1st I thought, "easy it's 20mins because it's double the time/cuts". But then I saw the numbers 2 and 3 and thought "wait no, it's a ratio" and I worked that out as 15mins. Then I thought "no, that's wrong. It's 10mins for 1 cut, so 20mins for 2 cuts! my 1st answer was right" And all this took place in like a minute.

[@TheEudaemonicPlague]

I find it hilarious that you admit this in public...especially the length of time it took you. It should be dead obvious what the answer is, and only take seconds to recognize. I failed 8th grade general math, and I had the answer pretty well instantly. Of course, I failed because I didn't ever do homework...I could do the math just fine.

[@garrettbates2639]

​@@TheEudaemonicPlague I find it hilarious that you feel the need to put other people down for second guessing themselves, and for not being as good at something as you perceive yourself to be.

[@nix_]

@@TheEudaemonicPlague Calm down, it's not that deep.😂😂😂 But good on you for feeling superior to me and boasting to people about how smart you think you are.👍🏾

[@fuglbird]

I'm glad you took your time and solved the problem correctly. I have helped many kids improve their math. When you stop them guessing, they improve very fast. You have solved it. Go!

[@screw_a_username7491]

@@TheEudaemonicPlague who asked

[@sicklysweetdenouement]

I will admit, it fooled me at first. It seems to be intentionally designed as a fun trick question, an awnser that isn't the first thought.

[@deadpenguin1]

Technically saying "I watched seasons 5 to 11" could be interpreted as not having watched season 11. You could be saying you started at 5, then watched up until 11 which would mean you stopped after season 10. That would be 5,6,7,8,9,10 making it 6 seasons. Saying "I watched seasons 5 thru 11" would then tack on the 11th season making it 7.

[@catcake]

How thick was the wood that it took 10 minutes to saw through? Was the saw blunt? The actual answer is 9 minutes to sharpen the saw, 1 minute to make one cut, therefore two cuts take 2 minutes.

[@l.clevelandmajor9931]

There was nothing about sharpening a blade in the problem. Also, if you've ever used a handsaw, you know most of them don't go dull in just one cut, two cuts, three cuts, or even several more. I am a woodworker, and these are things I know a lot about. I had a hand saw like the one shown in this video for forty years, and it never went dull enough to need sharpening in all of that time.

[@StevenHughestransportvideos]

​@@l.clevelandmajor9931 there is also nothing in the question about size of wood, which would affect the length of time. The true answer is "question needs more details to provide accurate timescales"

[@bigolbearthejammydodger6527]

bingo - this is not a maths question, its a systems analysis and workflow logistics question. using simple maths will give a wrong answer and teachers need to teach students when they can and when they cant use a simple calculation to get a meaningful answer. In this problem as presented there is NO WAY to get a meaningful answer to this question using just maths.

[@chaz720]

"Marie needs to stop skipping pull day."

[@Lylcaruis]

actually its 11 minutes because she needs to sharpen the saw first

[@_Vengeance_]

Ah, I see the teacher's mistake. The experience from the first cut will speed up the second cut. However, the dulling of the saw will slow down the second cut, evening out the speed-up from the experience. The teacher forgot to take the dulling of the saw into account.

[@Ensign_Cthulhu]

1:03 Teacher proving they've never picked up a board in their life or even seen carpentry done.

[@brianstuntman4368]

I suspect a teacher who went straight from being educated to becoming the educator, with no 'real life' job experience in between. To me, that was instantly a practical concern regarding the amount of work involved so I focussed on the number of cuts required.

[@MeemahSN]

@@brianstuntman4368 Even then, did they not do any kind of woodwork in high school?

[@rigen97]

they seem to have never done anything in their life ngl never cooked, never did handicrafts, never ate a kitkat, never shared a bar of chocolate...

[@grimmspectrum1547]

And I don't think any of you three succeeded in math because the teacher is right

[@youhangaroundforaliving]

How​@@grimmspectrum1547

[@Lewbugsyeetgang6098]

Bro worded it wrong at 8:00 acorrding to the wording he watched 5 TO 11 not THROUGH 11 meaning acorrding to the wording in the video the answer is 6

[@TheFinalMB]

Looks like his “correct” was …. Off-By-One!!! But yeah, came to say the same thing 😛

[@Mephistahpheles]

Many off-by-one errors can be easily avoided by simply counting the right thing: Fence posts: count the posts NOT the gaps Cutting logs: count the cuts NOT the pieces So, if the student showed his work (as students are usually directed): 2 pieces requires 1 cut 1 cut took 10 minutes 2 cuts takes 20 minutes 2 cuts will produce 3 pieces, as required Froggy: Day 1 achieves 3 feet (albeit, temporarily) (day 1) + (distance remaining)/(distance per day) = days required = 3 + (12 - 3 )/(3 - 2) = 10 In other words, consider the _max_ reached each day, not the outcome each day. Although this seems more or less the same as considering the last day in the sequence as the special case....often in math (particularly with infinite series!), one can't consider the final case nearly as easily as the first case.

[@douglasbrinkman5937]

that teacher has never cut a board in half.

[@Sagryl]

Nope. They spent their childhood and teens being an average/nerdy kid, without doing anything interesting like DIY projects, then cashed in on their lack of ambition and got a teaching degree. And this is where it got them. Yay.

[@w-lilypad]

Yeah, they don't have time since they're always waiting to cut a board to one piece

[@davelordy]

The only thing they've ever cut in half is - something something, rhythm of a joke.

[@peterbaruxis2511]

Nobody said half, just two pieces.

[@TayWoode]

@@davelordy.....is a large cake, half for now and half for later coz we all know they’ll be fat with blue hair and a nose piercing

[@Erik_Danley]

For the final one about the frog, I was thinking 12ft being the top, that’s not quite OUT of the well, meaning the frog would need another day. But I get the point

[@firstclaw1]

@@Erik_Danley I was wondering if reaching the ledge enables it to hold on to it and climb out, or if it needs to jump higher than the ledge to clear the hole. So, depending on that it takes one day more if it needs to jump higher than the rim to make it out.

[@XtreeM_FaiL]

It is in a super position. You should not look at the frog on day 9.

[@gg1k]

yeah that's the problem with contrived problems such as that one. not carefully worded enough to have a single reasonable solution.

[@jrstf]

First, the side of a well is vertical, the frog is going to return to the bottom after each jump that doesn't get it out. Second, since the frog is jumping vertical, it will never get over the edge, just above the edge, then fall right back to the bottom.

[@DonDueed]

Well, assuming a perfectly spherical frog...

[@7rich79]

The frog in the well threw me off...by one...of your correct answer, but the way I interpreted it the frog had to jump _out_ of the well, not just reach the top of it.

[@brandonfeingold4116]

The frog would have to jump more than 3 feet to get out on day 10, but it is only almost out. On day 11 it would be able to jump out of the hole.

[@7rich79]

​@brandonfeingold4116 yes, that was my reasoning too.

[@futurepath]

You were off by one 😆

[@tyranmcgrathmnkklkl]

@@3057luis Day 9 = 11 ft

[@MLennholm]

@@3057luis You're off by one, you're forgetting that on day 9, the frog _starts_ at 8 feet, then jumps to 11 feet and slides down to 9 feet. The frog doesn't start at 9 feet on day 9, it *ends up* at 9 feet on day 9.

[@daviarcherbr1613]

No, actually all answers disconsider the fact that the board was submitted to a gravitational attraction of one piece to each other. Once the gravitational attraction ceases from one part another, the board can be cut slightly faster, so the true answer is approximately 19,9999998 minutes.

[@zchettaz]

I would respectfully disagree. If it's taking 5mins to make a single cut, then I would argue that we are talking about someone who is a true professional, that delivers quality workmanship, a genuine master of the trade. It's a person that will measure twice, then twice more with two different tape measures before cutting once... ... but more to the point, gravity won't be providing any assistance to the cut as this is someone who has several clamps holding the board down as it bridges across two workbenches that are perfectly square and braced with each other and has( a saw guide that's calibrated to 0.00° down two-centres of the cut line and can be executed to level of delicate precision which hasn't been seen since the Egyptian pyramids.

[@DrakeDenney-nd3go]

Teacher: you will use these in real life Also the teacher:

[@Johnny.Fedora]

It's confusing when you equate the units "cuts", "pieces" and "minutes." An implication symbol would be more appropriate than an equal sign.

[@igrim4777]

Potentially confusing, rather than confusing I'd say colloquial and below standard for a largely mathematics based entertainer where those symbols should have consistent meanings. Expressing this video's duration as 1.243 cuts is open to misinterpretation.

[@xl000]

You can make it somehow work if you consider that you only need off cuts of a given dimension. I know this is not what the problem states, because into doesn’t mean that, but this would make the number of cuts equal to the number of pieces. This may be what the professor had in mind.

[@douglaswolfen7820]

Agreed. It's not ideal. Too many people get the impression that the equals sign means "and the answer is" or "and the next step is", instead of meaning that the thing on the left is equal to the thing on the right I like to see maths as a world of facts that you can explore. You can follow the implications of those facts to find new facts, and investigate wherever you choose. Too many people treat it more like a set of procedures you're supposed to execute, often robotically. They see an equation like "x²=4" and they talk about how you're "supposed" to "answer" it, which is silly IMHO, because "x²=4” isn't even a question i feel like using the equals sign this way contributes to that kind of thinking. But then, that's always bothered me a little about Presh; he seems inclined towards that way of thinking about maths. For instance, he talks about PEMDAS as if it's an unalterable fundamental truth of mathematics, instead of a convention that we use to help us communicate mathematics

[@Tkt-kj8ex]

​@@igrim4777i can feel myself getting smarter reading this...

[@Johnny.Fedora]

@@douglaswolfen7820, also, it should be PE{DM}{AS}. Multiplication and division have equal precedence. Addition and subtraction have equal precedence.

[@obliviouz]

3:20 - so the teacher was bad at maths AND at english?

[@seanrodgers1839]

In computers, we start an index with 0, so at 15, we have a count of 16. I'm very familiar with the off by one issue.

[@sportbikejesus]

fence post issues in computer programming are not always related to that. Beginner programmers are taught to remember that counting is inclusive where subtraction is not. eg, `seq 1..5` will produce 5 iterations, not 5-1 iterations.

[@jrstf]

Not me, I'm a FORTRAN programmer.

[@mastick5106]

@@jrstf I remember working on a program which mixed FORTRAN and C++, some indices were 0-based and some were 1-based. Debugging that monstrosity was a nightmare.

[@wostin]

In the fence one, if you need to build a straight fence 30 feet long and space fence posts every 3 feet: you could say you need 11 fence posts BUT that would be assuming that you can exceed the 30 feet length of the fence by the combined width of the fence posts, or also assuming every fence post has 0 width. So, if you need to build a straight fence strictly 30 feet long and space fence posts every 3 feet (36 inches), then you could use 10 fence posts that are 3.6 inches wide: (10 separators (the separation the fences represent) -1)*36 inches + (10 fences)*3.6 inches = 360 inches or 30 feet Given that fence posts in real life do come at around 3.5 inches in width, using 10 fence posts for this scenario would come just 1 inch short of 30 feet, compared to using 11 which would exceed the 30 feet length by 38.5 inches or around 3 feet :p

[@HrKCA]

5 minutes to go find the saw, 5 minutes for each cut. Makes sense to me.

[@vegarddhli4924]

No need to go find the saw again, so still 10 min then. :-)

[@timcoley646]

It's 15 minutes because she already found the saw.

[@bolt2839]

🗿

[@pokechatter]

Those first 10 minutes also included the time it took to find the board? And now that the sawer knows where to get another…?

[@Pokerjinx]

8:14 actually, that's not the best way to explain this one. If you watched seasons 5-11, that means out of 11 seasons, you didn't watch 4 of them (seasons 1-4). Therefore, if you take the total number of seasons, 11, and subtract the number of seasons not watched, 4, you get 11 - 4 = 7, which means you have watched 7 seasons.

[@Bomartins]

Good point. There's also some variability in the interpretation of the phrase "5 to 11". You can argue that '5 through 11' means you watched the entire 11th season.

[@UTU49]

@Pokerjinx. I agree that the approach you've taken is a much more natural way of seeing the situation and understanding why the calculation must be done that way. 5 through 11 =/= 6 seasons.

[@Moon-do1vt]

That is a practical way to solve it but his way of explaining is still good because it visualized the cause of error. (It was by counting the difference and not including the starting point which is season 5)

[@MikeTaffet]

One could also take the philosophical approach that you can only ever turn one board into 2 boards. Now you have two new boards, and each one can be made into 2 even smaller boards.

[@graydanerasmussen4071]

-Or you can never cut a board into two, because if you cut a board, you have two HALF boards :D

[@bobagorof]

But the question states that Marie *can* turn a board into pieces of a board - so whether you or I are capable of it is irrelevant. Marie has the ability to do so.

[@graydanerasmussen4071]

@@bobagorof Spoilsport! Ruining a perfectly good philosophical discussion :D

[@maooooooooooooooooo]

2:24 say that again..

[@Boiled-Oden]

xD

[@annegerber1259]

God damn it

[@bennytennyson]

THE ONE PIECE IS REAAAAAAAAAAAAL

[@AnimateTheArts]

NOO

[@JewelWildmoon]

Thank god someone else thought it 😂😂

[@doughnatsu]

This is the very definitions of overthinking

[@JLvatron]

In the teacher's defense, the clip at 1:19 of the person sawing the board, really felt like it was 20 minutes long!

[@thatonefrenchguy937]

But 20 minutes was the student's answer...

[@JLvatron]

@@thatonefrenchguy937 Technically you're right, but it felt like an eternity, lol

[@objectmountainstudios]

This channel is one of the reasons why I love math.

[@RickyMaveety]

Problem is, while 1 cut creates 2 pieces, we are not told the dimensions of the second board, just that it is “another board”. So we are missing information. Assuming the second board is the same size as the first, it would be 10+10=20.

[@johnluiten3686]

The assumption would be correct as there is no point in the question if it was lacking information.

[@bornach]

Unless the board is in the shape of a pizza😅 If cutting a pizza into two pieces takes 10 seconds, how long would it take to cut a similar sized pizza into 3 pieces?

[@josephhaddakin7095]

​@@bornach15 seconds

[@RickyMaveety]

@@johnluiten3686 Which means there may well be no point in the question.

[@johnluiten3686]

@@RickyMaveety The dimensions may be assumed from the 2nd picture and the statement of “equal effort”. Now if the pictures are not to part of the puzzle, then perhaps. But I go upon what I see, not what I imagine.

[@JonGee420]

This is a prime example of needing the teacher to show their work.

[@PC-ni6bp]

I spent SO long looking at the thumbnail thinking you were saying the teacher was correct and was scratching my head

[@mikeguilmette776]

I had the frog riddle wrong, but not because of being off by one . . . for some reason, I assumed the frog would still slide back down at 12 feet. 🤣

[@NichtcrawlerX]

Indeed, reaching the top is not the same as getting out. To get out it needs to have jump distance left, after reaching the top.

[@evknucklehead]

Yeah, part of the riddle specifically said the sliding back happens at night. So if it's at the top on _day_ 10, it wouldn't have a chance to slide back down because it could just hop away before night came.

[@hassanalihusseini1717]

Yes me too! That is ambigious question.

[@UTU49]

MikeG. I think your interpretation is legitimate. Can the frog get out, if he has JUST reached 12 feet and will immediately slide back down if he does NOT get out? This is something that needs to be specified. If a real world situation was similar to this situation, it could go either way.

[@hassanalihusseini1717]

@@UTU49 Yes, may be the distance should not be a multiple of the climbing distance.

[@DrakonLameth]

I could be the smart-alec-in-class on the well point and argue 11 days for the same reason I'd tell someone who said 12 was off by one on their thought -- the well is 12 feet deep, so on day 10, the frog makes it to the surface, but doesn't leap *clear*, it leapt *to* the height of the opening, so one more day to jump clear. (Maths as "starts at -12, +3 jump, -2 slide, must reach higher than 0 to escape")

[@brianschuetz2614]

That actually crossed my mind as well.

[@stdprocedure]

This is one of the reasons I hated math on elementary/middle school I thought about 11 too, but these scenarios are always so weird, they require some imagination, but not complete imagination, or else you will be wrong and you will receive 80/100 while the smartie will receive a 100/100 and be praised by all school teachers...

[@jonahansen]

These are the type of counting issues programmers have to learn to solve quickly and accurately... I know from experience.

6:32 As an AMC competitor, I can attest to this that I made almost a hundred off by one errors in my history of practice problems

[@Zulfar-bd9tc]

The problem I have with that explanation of 15 minutes based on where you're cutting at the halfway point is that it doesn't answer the question. The question throws out different possibilities with where the cut is being made with the wood because the question states "If she works just as fast," which to me means that the time for the cut rate is set at 10 minutes. That is set in stone. So no matter how Marie cuts it, it will take her 10 minutes to make the cut.

[@fdmillion]

This is referred to as the fence post problem. Example: If the distance between two fence posts is 10 feet, how many fence posts do you need to make a fence 30 feet long? Answer is clearly 4 posts, but if you don't think about the fact that *each end* needs a fence post, it's easy to just do 30 / 10 = 3.

[@Grizzly01-vr4pn]

Didn't watch the video all the way through before commenting, eh?

[@ItsAsparageese]

​@@Grizzly01-vr4pn Someone got enthusiastic about sharing knowledge and acted on it right away instead of waiting a while first? Unacceptable, better snark at them for it :P

[@Grizzly01-vr4pn]

@@ItsAsparageese Yep, that pretty much sums it up.

[@ItsAsparageese]

@@Grizzly01-vr4pn I'm sincerely sorry for you about your weird priorities

[@Grizzly01-vr4pn]

@@ItsAsparageese Don't be. You have no place being sorry for me nor judging any of my priorities. You deal with your own business.

[@BobFitchKSP]

As a woodworker I can tell you that cutting a board that’s half as wide will not take half the time of the wider board. It’s way more than half, but less than the original. Each stroke of the saw cuts a certain depth. It’ll be closer to the original board time, as long as the saw can stay on the board for its entire stroke. Unless it’s a bandsaw or table saw… then maybe it’s half the time, not counting setup time, but the picture shown was of a handsaw.

[@Entification]

Why are we shocked anymore? This has happened so much it should be shocking if a math teacher knows basic arithmetic.

[@nameisname5566]

her answer is technically true if you cut it vertically.

[@inverse_of_zero]

hey presh, i think it's great that a lot of your videos explore not just concepts in 'pure' mathematics, but also issues in maths *education*. the latter i think is not only more accessible to a wider audience but is also far more impactful to society through our primary and secondary school teachers. keep up the good work in this space!

[@Chandichada]

This channel is wild. 😂 Sometimes I feel like watching a video about quantum physics is more understandable than what is shown here. Other times, like right now, I thinkk I am watching sesame Street. I love it ❤. Never change📚🤠😂

[@twostate7822]

Obviously if it takes 10 minutes to make a single cut in a board, you should go to the hardware store and buy a new saw with sharp teeth.

[@emeraldaly7646]

8:12 Or just do 11-4, since there's 4 seasons you haven't seen.

[@SerialDesignationM3094]

You're wrong about that last one. The frog has NOT gotten out of the well on day 10 as he'd need to jump OVER 12 FEET to get out. He gets out on day 11 because he jumps PAST the lip of the well. You did a fallacy as well.

[@debandmike3380]

so the frogs final jump in your illustration doesn't show the frog getting out it shows him hitting the edge. he would need another day to clear the edge. because you did say jump out.

[@Tomtraubert2009]

4:25 - yeah creative, but not the same board and cut as the original question. Marie won't be able to cut half her post longways, but, if she did then the long cut would take much longer and the answer would be greater than 15mins (in fact it'd be greater than 20 mins)

[@mimigaming9383]

But the problem never specified the shape of the board

[@AlarKemmotar]

Another (wrong) way of interpreting the problem is to imagine that you're cutting two smaller pieces off of a larger board in ten minutes. Then it would take 15 minutes to cut three small pieces off. The key here is that the problem states that she cut a board INTO two pieces, not that she cut two pieces off the board.

[@pysaumont]

The last one is wrong. Assuming (for simplicity) that nights last for 12 hours, the time needed for the frog to get out is 10 x 12 + 9 x 12 = 228 hours = 9.5 days

[@Carlos59706]

Interesting option, but i think there is not enough information to assume that the frog take 12 hours to jump because is not specified. "Every Day" means just to the number of the Day in which the frog is regardless of the hour, so i think 10 days is more correct, but even if you assume that frog jumps at first hour of the day, the answer will be 9.25 days, since the daytime starts at 6:00 am.

[@Zenvian]

I like how it's all because the 'cut' and 'board' are two variables that can be taken into context totally differently from the preferred way.

[@Hablas-hi6vl]

This is so obvious. I asked my 6th-grade students this, and the majority got it correct they got it right.

[@bobdear5160]

With a square board, with a first cut parallel to 1 (therefore 2) of the sides in 10 minutes, a second cut at right angles to the first cut can take anything from almost 0 to almost 10 minutes. The assumption is that the first cut bisects the square and so is halfway along a side. For a square which is s x s in size, you can vary the proportion between left and right sides from 0 to s, hence the infinite number of answers between 0 and 10 minutes! Other topological shapes are of course possible such as an annular ring (donut). I’m not going to hurt my brain trying to cut a Möbius strip lengthwise!! 😂

[@nurmr]

This also assumes all cuts are made at right angles. If you make a 45 degree cuts then through the center it could take just over 14 minutes to make the single cut, and over 21 if you include the second "half" cut as well. If you cut near the corners it might only take a minute or two to make two cuts and end up with three pieces.

[@bobdear5160]

@@nurmr and that it is a “thin laminar” to preclude any 3 dimensional cuts!! If it is thick, you can put a cut through the plane of the shape - you could have two identical pieces… think of cutting through a cube or other shape with height breadth and depth. The question didn’t say you couldn’t think in 3 dimensions (conversely it didn’t say you could). There is no limit to our imagination!

[@DonDueed]

You've ignored the grain issue. If you have only one saw, one of your cuts will be made across the grain with a ripsaw, or with the grain with a crosscut saw. That could make the second cut take longer than the first, if it's even possible at all!

[@bobdear5160]

@ I never was practical! Thanks for the wood specialist’s correction to a maths person’s rose tinted spectacles!

[@JoanSlugXAkaJerkyBogard]

Dear Marie. If you take too long to cut wood manually, Why won't you just use an electric saw?.

[@mathematicskid]

1:08 eventually everyone saw 😆

[@narfharder]

Good catch. I aspire to be you. IOW I saw what you did there.

[@ThatGuyWithNoLife]

When I was trying to solve the answer through the thumbnail, I thought it said 20 minutes was wrong, so I went into the actual video and it turns out I was not wrong 😂

[@christianbuche9244]

That reminds of what's called "Zaunpfostenproblem" in German (literally "fence pole problem"): You need n + 1 poles for a fence of n units in length

[@RGP_Maths]

The most noteworthy off-by-one error: people who celebrated the END of the 20th century at the BEGINNING of year 2000.

[@christophelemaire4551]

It depends where, in english speaking countries, the year 2000 can be called "nineteen hunded", which negates the risk of a mistake.

[@Argoneui]

That's just convention. Depends on where you start counting, nothing requires you to start at 1AD. In fact the ISO8601 standard specifies 1BC as year 0. That's the millenium normal people use.

[@Raderade1-pt3om]

Current century is 21st?

[@RGP_Maths]

@@Argoneui Yes, 1BC would have to be year 0, and by definition the present calendar system DOES start at 1AD (or 1CE as also in use). The first century was years 1-100 inclusive (not 1-99 as that's only 99 years; not 0-99 as year 0 isn't part of the CE calendar). 20 centuries = 2000 years, so the 20th century must complete at the end of 2000 years. If I put 100 items on the table and ask someone to count them, anyone who starts by counting the first item as zero, going through to the last as ninety-nine would be considered somewhat peculiar.

[@palladiamorsdeus]

Eh, it's a little confusing but let me see if I can clarify. 0-100 was the first century, it was counting up to the first hundred years. That means that 1900-1999 were the twentieth century, which puts us in the twenty first century. The first one hundred years were the first century, not the zero century.

[@trevpavey3505]

8:14 you could just do one extra cut from 5 cuts or 6 pieces for 6 cutsfor18 minutes because the question doesn’t say they all have to be vertical or horizontal

[@1a1u0g9t4s2u]

Another example of ‘off by one’ is to count backwards from 10 the number of fingers ( and thumb) on one hand. Answer is 6. Then add 5 as that is the number of fingers ( including the thumb) on each hand. 5 + 6 = 11 therefore you have 11 fingers and thumbs.

[@salliemagnaye1403]

Huh. I didn’t know this went so deep. At first, I thought about ratios and proportions.

[@runeguardian]

If it takes 10 mins to make 1 cut, it will take double that time to make 2 cuts at the same speed action.

[@mohitrawat5225]

Funnily enough once someone commented in one of your video saying that once teacher asked to solve this same question with different values and the teacher did the same mistake but when that person corrected the teacher, teacher's face was worth watching 😂😂😂😂

[@levi5073]

How is this complicated??? My God...

[@maxhagenauer24]

It's not complicated, it's just confusing wording and what the question actually means.

[@StevenHughestransportvideos]

It's complicated because you don't have all the information to provide a true and accurate answer. It doesn't confirm the additional cuts needed are the same size, and therefore, it could be quicker or longer for the additional cuts. Simply put, the question is a "how long is a piece of string" question

[@cowdyayaad6378]

​@@StevenHughestransportvideos What is the speed of light?

[@Alexandar358]

It's not it's just an easy trap to fall into

[@johnc3403]

@@maxhagenauer24 Effectively, this is a trick question. More about careful reading, observation and understanding than mathematical ability.

[@j.thomas1420]

Let's face it : Marie is not good at carpentry.

[@jumper233]

10 minutes to cut a board in half...you're fired.

[@abyssalreclass]

I work at a hardware store, and I am having immense difficulty imagining even the most inept of the individuals that management calls "customers" taking 10 minutes to cut a piece of wood

[@memyname1771]

It took Marie 5 minutes to find the saw, and another 5 minutes to make one cut to cut the board into two pieces. She now has the saw and another board of the same size as the first board. It will take 5 minutes for each of two cuts to make three equal size pieces. Therefore, the correct answer is 10 minutes.

[@johnburgess2084]

But after making the cuts she has to put the saw away. This takes another 5 minutes because she has to decide where to place the saw so it will take 5 minutes to find it the next time she wants to use it. So, the teacher was right --- 15 minutes!

[@benroberts2222]

Requires making assumptions not stated in the problem. If we need to account for setup and cleanup time the answer is underdetermined because we don't actually know how long that takes; we have one equation with two unknowns

[@memyname1771]

@@johnburgess2084 No, her husband had been using the saw and forgot to put it away, so she had to search for it. Normally, the saw hangs right here next to where she saws logs.

[@memyname1771]

@@benroberts2222 As has been explained by many before me, there are as many correct answers as there are assumptions that can be made to fill in the missing data. Is the second piece of wood the same size and shape as the first? Did she just clip off the corners of the second piece of wood? Was she tired after cutting the first piece of wood? The missing data precludes one correct answer. Therefore, the assumptions I make make my answer correct for those assumptions.

[@SomeCowguy]

Well, let me add that it never said into 2/3 equal sized pieces. We can assume the third piece can be a little corner piece that takes a minute. ​@@benroberts2222

[@Retrovorious]

6:16 I’m sorry but disagree that we should give the teacher a break. While we all do make this mistake at least once, it’s while we are still learning about elementary math problems. An actual math teacher in a school should know better.

[@matthewmartinez3550]

Actual teachers can make mistakes, it is how they react that matters. My teachers encouraged us to point out mistakes in the homework and/or test. I've had cases where a caught error became a free answer for the class. I've also had teachers who refused to either budge or elaborate on why they think they're right, so there are still casers where your point still stands, we just don't know which way the pendulum swings on this issue.

[@reubenmanzo2054]

I had a situation like that. The question was as follows: A ship is sailing due south. It turns to sail north east. Through how many degrees did the ship turn? The correct answer was listed as 45, with a diagram of the ship's travel path given as reasoning.

[@PineappleDealer37]

Ah, the backwards swimming ship. My favourite.

[@yy2bggggs]

Not necessarily. Though I haven't seen this diagram, from the description, this is entirely possible and checks out, requiring only forward motion.

[@whatisdis]

Just to be in the same page, I assume the actual answer to be 135 degree? Alternatively, 225 degrees if the captain aren't confident with doing a left turn a.k.a. port side. I would accept 45 if it's a car or the ship had a reverse gear.

[@yy2bggggs]

​@@whatisdis Where we diverge is that you're thinking of this as a test; and I'm thinking of it more like a puzzle. As a test there's some "right answer", but to get there, you have to make what I'll dub "reasonable assumptions". By contrast, as a puzzle, there's a thing that's being described accurately; to get there, you have to figure out what "reasonable assumptions" you're making are failing you. So to address your post, I'll describe one way to say what you're saying. Suppose I'm facing south; so my heading is 180. If I want to face northeast, I must change my heading to be 45. One way of doing that is to rotate clockwise by 225 degrees. Another way of doing that is to rotate counterclockwise by 135 degrees. By my reading of the OP here, we have a ship that is sailing due south; to me that describes a motion along a straight line. The ship then turns; and by my reading, to "turn" here means to deviate from a straight line. The way I'm reading this, the "answer" of 45 degrees is really just part of the "puzzle"; so we have the ship deviating from the straight line by 45 degrees. So by my reading, you are allowed two operations... to go in a straight line, and to deviate from going in a straight line. Your deviation from a straight line must be by the amount of 45 degrees. Using these two operations you somehow need to change your heading (assuming it's 180; aka your sailing due south is going forward) from 180 to 45. Mind you, this isn't exactly one I would put in puzzle books... but thinking about this as a puzzle may help you figure out what's going on here. I could draw a diagram! ;)

[@yy2bggggs]

@@whatisdis Apologize if there's a duplicate reply... I think my last attempt didn't take. But to be on the same page, here's one way to think about what you're describing, with caveats. If I am facing south, my heading is 180 degrees. If I am facing northeast, my heading is 45 degrees. In almost but not quite every situation, I can change my heading by rotating. One of the not-quite-every-situations is consistent with my having a heading of 180. Assuming pun only slightly intended that I'm in a position to change my heading by rotating, and am facing south, then I can change my heading to northeast by rotating clockwise 225 degrees or rotating counterclockwise by 135 degrees. If however I'm in that situation where I can't change my heading by turning, then those operations don't matter... regardless of how much I turn, my heading will always be 180, and the only way to change that would be for me to _move_. We can talk about maps as well; if I have a map such that going east is right, west is left, north is up, and south is down, as is canonical; I can imagine my location and orientation on that map. Those rotations can be thought of as spinning on some point in the map. That special location where my rotation will not change my heading, on this kind of map, if it's even on the map, is probably not a point, but rather a line; by contrast, that same location if I'm standing on it will indeed be a point. The reason it's a line on the map is because the map of this sort has to behave weirdly; or phrased another way, it's related to the fact that we're dividing by cosine of 90 degrees which is 0, so it's a singularity. But I digress. What were we talking about? Oh right. A ship. Okay, so we have a ship. That ship is sailing due south. I can't find anything about its heading, but I don't think it matters; we could say we're sailing in reverse if we really want to, but in that case we're still sailing south, as that's what the thing says, so our heading would be 0 but we're sailing in the same direction as if we were going forward with a heading 180 anyway. That's complicated, and I don't think it matters (the problem isn't to _face_ northeast anyway; it's just to _sail_ northeast), so I suggest just imagining us sailing forward anyway. So again we're sailing due south. Choosing my words very, very carefully... so long as we sail due south, we'll be going in a straight line. But there's another thing that happens... we turn. To turn in my understanding means to deviate from a straight path. By my _puzzle_ brain reading the OP, I interpret "the correct answer" as yet another specification; thus, I just take it to heart that when it says the ship turns by 45 degrees, it does in fact deviate from a straight path by 45 degrees. And apparently we do that "to sail northeast". In my puzzle like mind world where everyone's a perfect logician and what not, if the captain says he's turning 45 degrees to sail northeast, I trust him, but that implies that somehow, you can deviate from this straight path described as going south by an amount of 45 degrees and wind up sailing northeast. So the big question is, is that possible? And surprising at it may sound... yes, it's possible. To summarize, here are the parameters. 1. We start sailing south. This is a straight path. 2. We deviate from this straight path by 45 degrees. 3. Given nothing else unspecified happens; i.e., that all we do is _turn_ 45 degrees, and _travel on straight paths_, we will wind up traveling northeast. Somehow. Yep. It can happen. Need a diagram? ;) If you disagree, I'm almost certain you're making at least one assumption that is wrong.

[@joelturnbull4038]

I remember when I took a critical thinking class at uni. One day, we were given several “Is this possible” questions, one of which was as follows. “There are 101 people in a room. Each person in the room has a different number of hairs on their head to everyone else. The person with the greatest number of hairs has 100. Is this possible?” Some students got very emotional trying to explain to the tutor that he was wrong, and that the situation is not possible. He then went on to make a distinction between “counting from one” and “counting from zero”. This was a bit of a life-changing moment for me in the way that I understood the world. It’s so weirdly mundane, but I think about that lesson often.

[@Acrophyllia]

Immediate first thought: 10 minutes for 1 cut, 20 minutes for 2 cuts. -> 20 minutes to saw a board into 3 pieces

[@dentonyoung4314]

2 pieces = 1 cut, 10 minutes per cut, so 2 cuts = 3 pieces = 20 minutes. How did the teacher bollix this up?

[@_Codemaster_]

Well, because the teacher wasn't the sharpest tool in the shed.

[@jmkqfnvyl87]

Mary also needs to have her saw sharpened. . . 😅

[@randomperson2160]

Because the teacher took 10 minutes and divided by 2 to get 5, then multiplied by 3 to to get 15. Not realizing it is not the number of pieces but the number of cuts.

[@ersanylmazturk1761]

1:51 THE ONE PIECEEEEEEEEEEE THE ONE PIECE IS REALLLLLLLLLLLL

[@averagedude2002]

Can we get much higher

[@XJWill1]

I'd say the answer to the frog problem, as stated, is best given as 9 days. Yes, it would reach the top at the beginning of the tenth day, but since it is the BEGINNING of the tenth day, the duration of time was 9 days, assuming it started at the bottom of the well at the beginning of the first day.

[@tanvirrahman7339]

Day 1 starts are 0ft and ends at 1ft after the night so at the start of day 2, the frog is at 1ft. Day 9 starts are 8ft and ends at 9ft. Day 10 starts at 9ft, jumps 3 feet and frog is at 12 feet now. There is no indication on how long it takes to climb 3ft. 10 days is still the correct answer.

[@Becky_Cooling]

If we assume that the well is dry, the frog will dehydrate and die after about 7 days,

[@XJWill1]

@@tanvirrahman7339 No, it is 9 days. The frog "jumps", it does not climb. So at the beginning of the tenth day, it jumps to the top. So the time to get out is 9 days plus the length of time to jump. Any reasonable interpretation would put it at 9 days plus 1 second or so.

[@MrDannyDetail]

@@XJWill1 I don't think the frog is making a single 3 foot jump each day and then thinking 'job done until tomorrow'. I think the 3 feet is the overall progress it can make from a whole day's worth of jumping up the inside wall of the well. By that interpretation it gets out just before nightfall on day 10, so a duration of 9.5 days (or something in that region) could be argued to be the answer.

[@kmbbmj5857]

I have a different interpretation from that. When the frog jumps from 9 feet, it reaches 12, which is equal to the top, but not above the top so it is not out yet. It takes one more day to jump above the top and therefore out of the well.

[@monke4044]

Imagine getting confused by your own question

[@skeptic10]

I learned at school that you are not supposed to give the real answer but the answer the teacher expects.

[@gorilladisco9108]

You guys forget that Marie spent 5 minutes meditating and contemplating, then the other 5 minutes for actual sawing. So if she had to saw the wood into three, she would need 5 + 5 + 5 = 15 minutes. :p

[@LumemDH]

You forgot the cooldown exercises that she did after each cut, and the exercises sesh lasts 3 hrs. So it’s 5 min+ 5 min + 3hr +5 min +3hr =6hr and 15 min😊

[@All4mula]

10 mins because she did it just as fast

[@SpencerPhreak]

Final Frog question: WRONG!!! In order to get OUT of the well, the front needs to jump HIGHER than the top, which means it needs an extra day = 11 total days

[@LiveSeruio]

For the frog in a well the answer could also be 11 days assuming the well is exactly 12 feet deep meaning he would not get out by reaching 12 feet but rather has to jump above that

[@Nosregni]

OTOH it says the frog “can” jump 1 foot each day, not that it does. It might never jump, not even trying to escape from the well!

[@Baekstrom]

"Day 10: I finally made it to the top of the well... barely. I just reached the edge, saw the sun set, and then I lost my grip and slid back two feet. I don't think I can survive another night without food and water. I'm doomed!"

[@verkuilb]

@4:30 The torus answer is incorrect. The problem states, “…a BOARD…”. The definition of a board is, “a piece of wood sawed thin, and of considerable length and breadth compared with the thickness.” A torus is therefore NOT a board.

[@ngwoo]

He said a ring, not a true torus. A board with a hole in it is topologically a torus, still a board, and the math here applies

[@greebo6549]

But you can have a kitchen chopping board, or chessboard

[@elpapa68]

Well, according to that definition the square piece of wood is definitely a board.

[@verkuilb]

@@greebo6549 Not if you’re consistent with the illustration which was part of the problem.

[@Cobb]

The real tragedy is that it took Marie 10 minutes to make 1 cut

[@brianschuetz2614]

Keep in mind, Marie is a girl. Wait, was that misogynistic?

[@peterbaruxis2511]

Actually Marie had a coping saw- she used it on a board of an unusual shape and in only ten minutes, using only one cut she made a swan and a butterfly.

[@xinpingdonohoe3978]

​@@brianschuetz2614 excuse me, this is the 21st century. Girls can do anything guys can do. Eventually, anyway.

[@wendyg1059]

To be fair, for the fence posts, you may only need 9 or 10 depending on the thickness of the posts, since the total length on the fence shouldn't exceed 30'. Also, for the Murdoch Mysteries, you are incorrect in saying 7 seasons were watched because the question specifically states "5 to 11," not "5 through 11," which would imply the viewing stopped before beginning the 11th season. 😁

[@chocolatechip12]

This gave me flashbacks to my algebra teacher who would constantly assign us to do problems 10-20 for homework and insist it was 10 problems.

[@uli1956]

This is also a problem of wording: The problem statement does not mention the size of the board or the shape of the cut pieces, so any number can be a correct solution to this problem. For example, If the board is "long", e.g. 1 meter x 10 centimeters, and Marie's initial cut produces 2 pieces of size 1 m x 5 cm, this long cut might take 10 minutes. But then, if she cuts such a 1m x 10cm board into three pieces of width 10 cm and lengths 0.2 m, 0.3 m and 0.5 m, then she needs to do only two cuts of 10 cm length each, so the total time then is 2 minutes (provided that the cutting speed is the same in either direction).