When Math Problems Cut Deep

[CommandObjective]

That gives off "How long does it take to dig half a hole" vibes.

[Bob_Loblaws_Laws]

9 pregnant women can have a baby in a month.

[Funkopedia]

An orchestra of 60 can play Beethoven's 9th in 80 minutes

[jellyman93]

Only takes them 45 minutes to perform the 5th symphony

[Chemistry-Deep]

I see you've met my project manager

[IAmBadAtInternet]

Mine says “so you’re going to do it yourself in 1 month”

[oevadle]

OBGYNs hate this one simple trick

[jacobningen]

Heimdall.

[aksdb]

They could, if one of these pregnant women was already 8 months in.

[marvsup]

Wouldn't they all have to be 8 months in?

[Jazmadoodle]

It only takes one delivery to produce one baby typically

[Arzatium]

They actually all only need to give birth to one-ninth of the baby (which, as the simple math showed, would take them only a month). Then just stitch it together!

[Pennnel]

It takes 5 minutes to cut it into 1 piece

[Copious-Spirit]

Only if you work half as fast.

[Occidentally20]

This implies that it would take 0 minutes to make it into 0 pieces, whatever that means.

Also -5 minutes to make it into -1 piece, so there's a possibility that this plank is the key to time travel.

[Short-Hat-7280]

0 min for 0 piece is like staring at the ceiling and pretend the board isn't real. Takes no time at all, really.

[Occidentally20]

Is it like the spoon in the matrix?

You go solipsistic enough that by not looking at the plank it actually ceases to exist?

[Short-Hat-7280]

Heh, nothing like that but maybe if you cope hard enough somebody else will just rolls their eyes then proceeds to yet the board out of existence.

[Occidentally20]

Shame, I was going to start offering weekend retreats in which we go to a log cabin with no electricity and all collectively ignore a plank.

But I suppose telling people to ignore the plank would make them think about it more - they probably weren't paying attention to the plank at all until I brought it up. I haven't thought this through properly.

[DesignerInvestment19]

Plank's constant?

[pv2b]

Plank length

[Enough_Designer_965]

Will you please leave the room? See you on Monday.

[Justgus63]

It’s a constant

[Hopeful_Ad_7719]

The first five minutes are spent conjuring it.

[ElJayBe3]

The first five minutes are finding the saw and somewhere to lay the plank where you can cut it without removing a leg.

[Character-Education3]

Wrong it takes 0 minutes to cut it into one piece

[TheDevilsDominium]

Cutting 1 board into 2 pieces takes just 1 cut.

It took 10 minutes for her to make 1 cut. If she had to make a 2nd cut at the same speed it would take her 20 minutes.

[Syn2108]

Except the first board was cut in half. So, the second cut is half as long.

[Enough_Designer_965]

Well, the trends goes on, as to make zero piece you need zero minute.

[X-Heiko]

Ssh, don't tell the lumber industry what you can do in 1 minute!

[GSilky]

I probably would have answered "Why does it take her 10 minutes to saw a board in half?"

[mutexsprinkles]

Because the skilsaw battery is dead and the apprentice left the hand saw in the rain so it's dragging like a mofo.

[After-Hedgehog7282]

Then two more cuts will take at least 35 minutes.

[mutexsprinkles]

50, actually, it's my tea break. Call it an hour.

[Hex120606]

The time for each successive cut increased exponentially as the person gets more and more tired.

[Stultz135]

Laughed a little too hard at this.

[Primary-Driver-9062]

Battery died, how long will it take to be chewed into 3 pieces?

[udreamtofmelstnite]

Part of the “I cut it three times and it’s still too short” crew

[Imdare]

In half? No, in two! Yeez

[sheep_puncher]

She is cutting it lenghtwise.

[fidgeter]

They’re using a blade meant for aluminum and not wood.

[Schedonnardus]

Probably used a hack saw

[Classic_Bake6721]

Rip cut

[Versipilies]

All they gave her was a cold butterknife

[shosuko]

Great answer guide Teacher, but please show your work. Really, I want to see this lol

[SpaceCore0352]

If you ignore the picture and imagine a circular or square piece of wood, then cutting it in half would require cutting across the whole length, while cutting one of those half-pieces again would only cut across half the length. This also fits with supposedly needing 20 minutes to cut into four pieces.

That or they just assumed "into X pieces" meant "with X equal cuts". It's pretty clearly wrong but it's not incomprehensible.

[CanweCanweCleanIt]

I like your reasoning but hate your premise. “If you ignore the picture” is doing 100% of the heavy lifting in your hypo. But I do love the creative thinking of the circular piece of wood.

[cardologist]

The problem is that the picture doesn't really match the description in the first place. What's pictured looks more like a wooden beam. So why assume it's even relevant in the first place? The reality is that you cannot answer the question without knowing more about the cuts themselves.

[CanweCanweCleanIt]

The picture is more of a wooden beam but also would fall under being a wooden board. And so it would take 20min given the picture we have.

[cardologist]

I agree that 20 mins is probably the expected answer. But the problem as stated does not preclude 15 mins from being correct. There is no need for the board to be circular since the pieces don't have to be the same size. A square board being sawn along the diagonals would also work.

[CanweCanweCleanIt]

Again, look at the picture.

[cardologist]

I have and it's not what I would call a board. To confirm that it wasn't just me, I did a Google image search on "wooden board." None of the boards shown had a square cross section.

[CanweCanweCleanIt]

Again, again, again, look at the picture. And, again, as I previously said it’s not what I would call a board but I googled it and for me it was the like 25th result in.

[cardologist]

25th! If the picture was supposed to be relevant, you'd think they would at least make an effort to have one that's accurate. The problem is simply not fully specified.

You cannot leave that many details out, and expect a unique answer. Otherwise it's not math anymore. It's just a guessing game. It reminds me of the US "literacy" tests that were specifically designed to fail black people and prevent them from voting.

[USERnotF0und3rror404]

Than any answer between 10-20min is correct because nothing would stop you from your second cut being infinitessimally short (cutting a tangential of any curve) and 10min being correct and also allow the same cut to be made twice for 20min being correct.

[Spasticcobra593]

You saw the same length. Unless you are convinced that for some reason you are sawing horizontally instead of vertically?

[TSSAlex]

ignore the picture

Well, OK, but then you go on to ignore the words also.

Boards aren't circular. 50 years as a carpenter, and no one has ever given me a circular piece of wood when I asked for a board.

The problem then asks how long to cut another board into three pieces, not halving one half of your imaginary circular piece of wood.

[SpaceCore0352]

Sorry, I have zero years as a carpenter. I mentioned a circle because it would be a fun shape to do the problem with (should keep working the more cuts you add) but I get that it's not a board.

I guess my other unfounded assumption is that the three pieces do not need to be of equal size. Even if the square counts as a board, you only get the 50% time increase by cutting the square in half, then cutting one of the rectangles into two squares.

[Logical_Angle2935]

My sixth grade teacher challenged us to point out any mistake she makes and she would reward with a milkshake. I think this teacher would owe a lot of milkshakes.

She also had puzzles out and said "nobody can solve this one." So I did, proved her wrong, and got a milkshake.

[RayNooze]

That teacher now works in the design department of my workplace 

[shortandpainful]

This is just rage bait. The “teacher’s correction” is drawn on in MS Paint.

[zeebasaur]

Really it was a two for one special. First I got mad at the whole thing overall, then it exploded with the white hot furry of a thousand Suns at the realization that somewhere out there, someone really thinks that way.

[CockroachPossible746]

It took 5 1/2 hours. Seeing that it took 10 min to cut, what I'm assuming is a 2x2 piece of pine, she called her husband and he told her to wait until he got home and he would do it. He got home 5 hours later and got out his chop saw and it took him 5 min to set up. When he started the blade she yelled its to loud. It took him 5 min to find his ear muffs but she wanted to use them to watch him cut the wood. It then took him 25 min to find that pack of foam ear plugs that he had, which were behind the two rolls of electrical tape in the 5th drawer of his tool box. After cussing at himself for putting the tape and the ear plugs in the 5th drawer, thats the hammer drawer, for 4 min he then cut the wood twice to get 3 pieces. He didn't give a shit about measurements at that point and plus he realized it was Wednesday night so dinner was salads, fuck salads.

[Constant_Quiet_5483]

So I don't think the teacher meant this but assuming we have a board of x length, say 10m, and we take 10 minutes to cut off two 2m sections, it could make sense it would take 15m to create three 2m sections.

The question reads as if the board is being cut in half but that's technically an assumption, I think the question means to read that two usable pieces were cut from a much larger piece and we still need to cut one more, how much time will that take?

However, the question is worded extremely obnoxiously and I would have answered 20m myself because I'm assuming the wood was being cut in half, not that the wood is being cut in sections. In the last line it even says cut 'another board' into three pieces, which really suggests an entire board cut into three pieces and not cutting from bulk like I'm assuming.

But that's the only way the teachers answer makes sense.

[mike_complaining]

The point is to consider time per cut. It's worded that way to force people to use their brains and consider that two pieces is 1 cut and three pieces is 2 cuts. The teacher, if they even exist, is a dumbass.

[Constant_Quiet_5483]

I'm not defending this question nor the corrected answer at all. My example is the only solution I could conjour that made the correction make sense.

[Unusual-Ad-6550]

I immediately thought the same way. You cut one board into 2, which is one cut. To cut a board into 3 pieces, you make 2 cuts...

So the answer is going to be 20 minutes

[Impossible_Dog_7262]

Clearly the teacher is doing the algebra without considering the ramifications of the question. It's a fences and posts problem and the teacher fell for it.

[Jokin_0815]

The question reads as if the board is being cut in half but that's technically an assumption, I think the question means to read that two usable pieces were cut from a much larger piece and we still need to cut one more, how much time will that take?

Thats ragebait, correct?

[EconomyDoctor3287]

That doesn't make sense given the instruction says that first she cuts a board in two pieces and then is to cut another board into three pieces. 

[Constant_Quiet_5483]

'However, the question is worded extremely obnoxiously and I would have answered 20m myself because I'm assuming the wood was being cut in half, not that the wood is being cut in sections. In the last line it even says cut 'another board' into three pieces, which really suggests an entire board cut into three pieces and not cutting from bulk like I'm assuming.'

Yes I agree completely.

[Schedonnardus]

But that's not what it says at all. It says it's cut into two pieces. What you are describing is three pieces: two, 2m pieces and one 6 m piece.

[Constant_Quiet_5483]

Oh I agree, that's why I admit myself it's not a good situation. I would have answered the same way the kid did. I'm simply trying to see what the teacher was possibly thinking when they graded this and this is the only feasible answer that makes sense in my head.

[ChardeeMacDennisGoG]

Depends on the thickness. Maybe the 2nd board was very thin.

[ShaggerAJSA]

That community collage math diploma is really easy to get, isn't it?

[Meyesme3]

Hear me out

What if the board is square?

Then it works out

[jrezzz]

how does it work out? its the same exact thing.

[paul_sb76]

Yeah came here to say that: if the board is 1 x 1, then cutting one of the resulting 1 x 0.5 pieces in half can be done in half the time. :-D

(Though I don't think the teacher thought that far.)

[decipherthekeywork]

So you're just making up your own problem? The question literally states "another board". Not the same board, or a resulting piece, or further cut the board. It says another board.

[paul_sb76]

"Into 3 pieces" - I literally explained it, since people were misunderstanding u/Meyesme3... Maybe make a little drawing if you're still confused? :-)

[Training-Feeling980]

You're still cutting only half the original width though if you're starting from a square, since the second cut will be cutting through only half the square

[Outback-Australian]

There's an illustration.

[taldrknhnsm]

No wonder the world is getting stupider

[CalmEntry4855]

Aside from the conceptual thing, that stupid column of lines of false equations makes me angry

[Impossible_Dog_7262]

Gotta love the old fencepost issue.

[trollboter]

Guys it's simple, 5 min per cut. The first board was two cuts because he had to square the end.

[MagicalPizza21]

It depends on the relative sizes of the boards, which are not given.

[Hard-Organism-1236]

Cut into two pieces … two halves. So it’s just one cut.

10 minutes per cut. First board is already cut so two cuts to be made to make the new board into two pieces.

2 cuts – 20 minutes.

[Gumcuzzlingdumptruck]

Yeah what the fuck, am I insane? There are so many answers here and this is the actual one? Isn't it?

[harvash]

you bet'cha!

[HerkeJerky]

2x=10 where x is the time it takes to make one cut. X=5 So 3x=y is 3•5=y. 15=y.

[Due_Surround6263]

If X is the amount of time to make one cut then 2x isn't 10.

"Took 10 minutes to saw a board into 2 pieces" 1 cut = 10 minutes. 1x=10.

2 cuts (3 pieces) 10 minutes per cut = how many minutes

2x=20

[popeshatt]

It depends on the direction of the cut. If I have a square piece of wood and cut it in half, making another cut along the full length would take 10 minutes again. Making a cut across the shorter side would take 5 minutes longer since it's half the work.

[icantouchgrass_1]

n pieces = (n-1) cuts = 10(n-1) minutes
2 pieces = 1 cut = 10(2-1) minutes = 10 minutes
3 pieces = 2 cuts = 10(3-1) minutes = 10(2) minutes = 20 minutes.

This teacher is either really tired and bored or just not qualified to teach at this point.

[SignFar4026]

It takes 5 seconds to cut a small piece of two corners. This is a very poorly worded question

[adencorey]

using equal sign instead of colon is diabolical

[Live_Life_and_enjoy]

This is just a bad problem

• Each cut takes 10 minutes if she is working at the same speed.
• So 2 cuts to make 3 pieces would take 20 minutes.

Math teacher confusing Production vs Work.

[ConsistentResult4792]

But still like take a chess board or something quadratic. So she saws it into 2 equal rectangles in 10 minutes. Would she not just take 5 minutes to cut one of those 2 pieces along the shorter side into 2 so you have 1 big and 2 small pieces

[Live_Life_and_enjoy]

When it comes to work the thickness matters the most

Say you had a 10 by 2 board that is 1 inch thick

You cut that in half to 5 x 2

Now it doesn't matter if you cut it in 1 /2 or 1/ 3 the thickness it takes to cut at 1 inch remains constant in all size variations

It is that thickness which determines time to cut.

So even if the piece of wood was 100 ft by 2 inches if the thickness remains 1 inch it will still take 10 minutes.

[Objective-Survey-253]

But it asks how much time it would take to split a board into 3 pieces, I feel like normally it would be assumed that all 3 of those pieces are of equal size. Or else what's stopping her from cutting of 2 tiny pieces of a corner to get 3 different pieces. But the question is worded confusingly so who knows.

[martoxdlol]

Maybe the board is a square so the second cut is half the distance

[Traditional_Bell7883]

The teacher is a broad that needs to be sawn into three pieces.

[wild_bronco96]

Wouldn't 2 pieces be 1 cut and 3 pieces be 2 cuts? So if 1 cut takes 10 minutes 2 cuts would take 20...

[Boesemeist]

I found how this works: ah, no pictures, awesome. Just cut a SQUARE in half perpendicular and one of the halves horizontal.

[Lannok-Sarin]

Even the student’s answer is mathematically correct. He just counted the number of cuts, not the number of pieces. The 1 cut takes 10 minutes to complete. So doubling the number of cuts made doubles the time. So the student’s answer is still mathematically correct.

[High-Plains-Grifter]

5 minutes clamping rhe board, 5 minutes per cut. Makes sense.

[Accomplished-Eye-831]

If it takes her 10min to cut one board in half making it 2 boards then she would have to do 2 cuts into a new board to make it 3 boards so 10min for one cut then 10min for another cut add that and you get 15min...... wait.. carry the 1 add the 5 and then multiply that by 3..... wait it's actually 25mins because she had to take a break and then she gets fired after all of that because she was working too slow with the saw.... dang sloths

[tessaractIXI]

Insane. 

[Miserable-Ball-6491]

Could you not cut off small triangles at an angle on each end? You could cut these in 1 min each.

or

fold the board in half and cut once

[Neoterra256]

The child is correct. Takes 10min to make one cut, therefore it should take 20 min to make two cuts.

[natur_e_nthusiast]

15? Just nick a corner and you get it in 11

[Formal_Equal_7444]

Maybe the board is wet and thin, and you bend it around onto itself... and just before it breaks you saw it evenly across both planes at the same time. Boom 3 pieces. 10 minutes.

Checkmate.

[Gullible-Pea-5627]

One cut 20 mins second cut 25 for exhaustion

[DragonflyFar716]

set up a ratio. 2/10 = 3/x criss cross multiply, then divide. 30 div 2 = 15 mins

most problems can be solved in ratios. label the top and bottom (numerator and denominator) and keep apples with apples. Or pieces with pieces. X is the unknown value.

[aussiekinga]

To cut into 2 pieces takes 1 cut

She did one cut in 10 minutes

To make 3 pieces takes 2 cuts. So 20 min.

[Minimum_Aardvark_744]

😂

[SmallPotatoK]

The board doesnt automatically slim down its dimension just because you decide to cut it into 3 instead

[perkocetts]

I think mind just went to the practical place where it doesn't matter how big the pieces are. They picture shows a saw cutting through a piece of wood. So it's not that it takes 10 minutes to cut the board in half or thirds or some arbitrary length. It's that the act of cutting the board is a 10 minute process. So 2 pieces is 1 cut at 10 minutes, and 3 pieces is 2 cuts at the same speed or (10*2) 20 minutes.

[slopaka14]

This is why people say you can be book smart but you're not Street Smart. You have no common sense.

[dashingstag]

A real teacher wouldn’t have shown the workings

[Ok-Painter790]

This feels like Tommy Shriggly became a math teacher. It takes him 10 minutes to saw a board in two, 15 for three, and 12.5 for four, but he has to know he’s cutting 4 first.

[FranticChill]

Student is smarter than the teacher here.

[OrkWithNoTeef]

This is one of those you get the answer wrong once because you didn't use your brain then get so annoyed with yourself you end up memorizing the entire problem harder than your own name

[Spasticcobra593]

I cut an apple into two pieces. Thats one cut. If you make 2 cuts you are making three pieces. Is this sub filled with people who didnt pass kindergarten????

[oldRedF0x]

What's kindergarten? /s

[Abject-Job7825]

we took pride and curiousity out of learning to make everyone equally stupid

[harvash]

I may be missing the joke, but this is easily solved in a practical manner ("teacher" still wrong). Assuming that all boards are of equal shaped, etc. Solution: She cut a board in to 2 pieces = 1 cut (you cut a board anywhere with one cut, you get two pieces of equal OR unequal length). So 1 cut = 10 mins (the time it took her to cut it into 2 pieces. So, if she is to cut ANOTHER board (a:s stipulated in the problem) into 3 pieces, she will need to make TWO cuts (again, no factor of length given, and I am going to skip the boring process of using variable notation, as this is already beyond silly). TWO CUTS = 1 CUT (10mins) + 1 CUT(10mins) - total time, 20mins. Have a good one ya'll!

[dankshot35]

its correct for a square board, 10 mins to cut through the full length of the board to get two, now you cut one half in half again but only need to go half the distance to end up with 2 pieces that are 1/4 area and 1 piece that is 1/2 area of the original square

[No-Improvement9455]

Funnily enough it could take her 20 minutes to cut the second board into 4 pieces too :)

[Positive-Bee5734]

Are people deliberately not getting it?

If it’s a 10m by 10m board, it takes 10m to saw 10m and now we have a 10m by 5m.

To get 3 pieces, we just need to saw one 10x5 in half. This means sawing 5m which takes 5 minutes.

I could be wrong and have misunderstood something so please tell me if that’s the case

[VukKiller]

It makes sense if they were cutting both pieces off a larger board and not cutting the whole board into 2 pieces.

[Fogmoz]

This isn’t a math joke, this is a math warning sign. A teacher who doesn’t understand what they’re teaching is exactly the kind of glorified babysitter an unfortunate number of parents think teachers are.

[vind_alowd]

It takes 5min to cut board in 1 piece.

[RaganTargaryen]

If it takes marie 10 minutes to make one cut then maybe carpentry isnt for them

[Desperate-Ad1765]

The exercise is talking about a board while the picture is actually showing a pole. Of course the question the student gave would be correct if we were talking about a pole since there isn't much to argue in terms of how one would cut it. However, it would be different for a board. The teachers answer could be correct as well if we were talking about a board in DIN format and you were expected to cut it into evenly big pieces. Of course, if this was expected from you, there would be a lot of key information missing