A Simple Riddle You Probably Will Get Wrong. The Watermelon Paradox!

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A Simple Riddle You Probably Will Get Wrong. The Watermelon Paradox!

Рет қаралды 135,273

Ай бұрын

Even people who have PhDs in science get this simple brain teaser wrong! Can you figure it out? (It is also known as the potato paradox.)
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Пікірлер: 759

@PeterFrancisFernandez Ай бұрын

The false assumption is that there is a 1% loss of water versus the original weight, when in fact it is only a ratio. Using that it becomes easier to understand that youre trying then to work out what weight fits the new ratio rather than thinking of it as having lost 1% of water

@TheOreoOverlord Ай бұрын

Yup, once understanding this, the problem becomes much more simple and obvious. Took me some time though because it's worded(quite well) to lead you to believe the % is not a ratio but rather an ammount

@Christopher._M Ай бұрын

I knew it felt like I was missing something when it first thought about it. Which is why I was sure you would have to solve algebraically to get it but it's such an easy assumption and mistakes to make if you just read it

@senseibear2436 Ай бұрын

Somebody is cheating here with the wording! I could have sworn the video said 99% of the total weight (100kg) was water.... Or is that what the listener just infers themselves, hence the riddle? It just sounds like the person removed 1.01% of the total weight...

@stevemaurer8120 Ай бұрын

It's not a "false assumption". It's an incorrectly specified problem. And that's the real answer: "As specified, this question is too ambiguous to solve".

@brevitygreaves2321 Ай бұрын

"dropped to 98%" means what? Is there an actual 1kg watermelon anywhere in the world such that, upon extracting 1% of its water content, its weight magically drops to 50% of its original weight?

@matthewedwards9423 28 күн бұрын

This sounds more like someone trying to come up with an excuse for why they ate half the melons on the train.

@micahlong2073 20 күн бұрын

But only the water!

@mayukhintesarislam306 9 күн бұрын

lmao

@NetherFX Ай бұрын

❌i've done half my tasks ✅my performance went from 99% to 98%

@HxTurtle 28 күн бұрын

not the same statement, though.

@TheTrueM4gg0t 7 күн бұрын

Not quite. Like this: ❌ Boss, I sleep only 98% of the time on the job now, instead of 99%! ✅ Boss, I doubled the amount of work I complete every day, I need a pay raise! 💸

@kubastachu9860 6 күн бұрын

@@HxTurtle yeah, more like "I'm doing less than half the work but only lost 1% of performance, yikes!" followed by "but why do you let me go with such good stats? Lost trust? How am I not dependable enough to not assign those tasks?"

@PugganBacklund Ай бұрын

my mind went: melon went from 1% -> 2%, doubeling, so weight must be half. then i started think, what did i miss..

@vt2788 Ай бұрын

You are just genetically superior

@southernbreeze3278 Ай бұрын

didn't make sense to me 'till I read this comment

@emad3241 Ай бұрын

you got lucky

@marvhollingworth663 Ай бұрын

You missed nowt, that makes perfect sense.

@user-jc2lz6jb2e Ай бұрын

You focused on what WASN'T water, yet the water is the focus of the question (all the information is in terms of it). People think "oh 99% to 98% isn't much loss", and that's where they get tripped up.

@Ynook Ай бұрын

The way I see it basically what you did in the end. If 1 Kg of watermelon is now 2% of the weight, the total weight is 50 times 1 Kg.

@theglobalwarming6081 Ай бұрын

I solved this myself. I am both confused how much weight was lost but also it kinda made sense

@scottmcmillen3015 Ай бұрын

Your method is far more intuitive to me than the ones Presh started with. First notice that 1%, hence 1 kg, is not water. For 98% water, we ask: “1 kg is 2% of what?” This question gives the intuitive answer 50 kg, or can be translated into the equation 1 = .02x, and hence x = 50 kg.

@ModelLights Ай бұрын

@@theglobalwarming6081 'I am both confused how much weight was lost ' Realize, there's an easier way to see the reduction in weight, take it further. 1kg solid and 99kg water gets the 99% water content. But to get to 50% water content, you have to have the starting 1kg solid, and only 1kg water left. You have to lose 98kg of the initial 99kg to get down to 50% water content. The water content percentage being referenced to the 1kg solids instead of an independent reference means the scale slides, and by using 1%/99% to start, the scale slides very hard. 99 kg of water is 26.12137 gallons. Take five 5 gallon buckets of water and another gallon, put them together, and try to wrap it all and hold it together with only 1kg of watermelon skin and rind. It's a not real problem, specifically chosen to use the self referencing 'water content' with an unrealistically high water content to generate the huge swing in values. It could work in some less familiar things, but you would be hard pressed to do this with a watermelon. Real watermelons tend to be 4% or so solid, they'll be mush before you get to 1%.

@michaelallen1432 Ай бұрын

That's pretty much what I did. The water is the thing that changes and it's the unknown. But the mass of everything else is the same before and after. You start with 100kg total, 99% of which is water. So everything else is 1kg. The amount after, is still 1kg. You are told that the water content drops to 98%. So that means the percent of everything else is 2% Knowing that the amount of everything but the water is 1kg, and that the percentage of it is 2% , you can then calculate the total mass of everything as 1kg/0.02 = 50kg

@beepbop6697 Ай бұрын

@@ModelLightsfrom what I'm reading, watermelons are 92% water. Perhaps if you remove the inedible green rind then the editable red stuff is 96% water...

@theoroth6515 Ай бұрын

From 6:26 to 7:07, there is the expression "d=0.1(100)=1" but it should be "d=0.01(100)=1"

@budsellers Ай бұрын

Your math solution is correct, but that freight shipping cost will be wasted because the load of watermelons are useless now

@martinprince8253 Ай бұрын

Watermelons that are twice as sweet? gimme gimme gimme

@dirkbester9050 Ай бұрын

Not at all. You can still make watermelon skin jam from it, and the concentrated watermelon juice can be drinkable. If it is not some kind of maidenless pit free melon, you can plant the seeds next year. Unless it also rotted. That would leave you with making some watermelon wine or vinegar at best.

@wideeyedraven15 Ай бұрын

They are not useless.

@angrytedtalks Ай бұрын

Bowling balls.

@adb012 Ай бұрын

The watermelons will not be dry. They are still 98% water. And they will be twice as sweet and flavorful.

@MichaelPiz Ай бұрын

But how old is the driver?

@isambo400 Ай бұрын

And how freshly does his toad walk?

@Bob94390 Ай бұрын

Because he has neither a fish.

@dirkbester9050 Ай бұрын

The driver is 98, but real thirsty!

@Sqrt.Infinity Ай бұрын

But how old are the watermelons?

@milanstevic8424 24 күн бұрын

But how many watermelons were there?

@mickdavies5647 Ай бұрын

They are students at a barbecue. I can think of several reasons why they got the answer wrong, ranging from 4.5% to 40% in volume 😂

@cparks1000000 Ай бұрын

😂😂😂 Some even 65%.

@TitularHeroine Ай бұрын

😂😂

@hedgehogclaws8877 Ай бұрын

This was actually hilarious

@jimmyh2137 14 күн бұрын

I can thing of some other reasons. More... plant based, let's say.

@9_1.1 28 күн бұрын

simple explanation: assuming the non-water part of the melons didnt change, that part is still 1kg. that 1kg is now 2% of the total mass, or 1/50th, meaning the rest is 49/50ths, or 49kgs.

@k1ry4n Ай бұрын

If the non-water content goes from 1 (1% of the original mass) to 2% of the new mass it means that we lost half of the original mass. If 1 kg now is 2% the new mass is 50 kg.

@aidanhammer6968 Ай бұрын

This is a much clearer way of framing it.

@k1ry4n Ай бұрын

@@aidanhammer6968 The explanation in the video seems to me unnecessarily complicated.

@SigFigNewton 15 күн бұрын

Wow. Nice! I wrote out three very simple equations with three variables and did the algebra

@SigFigNewton 15 күн бұрын

Looks like the video basically did what I did. U making me feel foolish

@ExtraTrstl 5 күн бұрын

This helped, thank you!

@ThinkOpenlyAtGMail Ай бұрын

You have the calculation of "final dry weight" misrepresented at 6:34. It shows "d = 0.1(100)", when it should show "d = 0.01(100)". (FYI)

@wild_insomnia Ай бұрын

damn,but it's headscratching how flabby dried out potatoes can still consist of 98% water...That's something surreal...

@jensraab2902 Ай бұрын

To be honest, a "potato" containing 99% or even "only" 98% of water wouldn't be much of a potato. Even watermelons, according to Auntie Google, don't consist of 99% water. The figures I found on the quick was 92% water in a watermelon, and 80% in a potato.

@beepbop6697 Ай бұрын

... And adult human male is 60% water

@tomdekler9280 22 күн бұрын

@@beepbop6697 Well yeah, both give a big wet splat when you chuck them out of a 12th story window.

@sheshakrishna1111 Ай бұрын

Chemical Engineers: Material Balance....

@sauerjoseph Ай бұрын

Yes, as a fellow ChemE, I was thinking the same thing. This is what we do every day. No decent ChemE should ever get this wrong! We know from experience how much minor changes in %concentration can make such a huge change in lbs total removed. Presh could have plotted an X-Y chart of "Change in total weight" VS "Starting %Water" (1% drop in %Water at each point) and use this to show how this 'change in total weight' heavily depends on the starting %Water.

@educassus Ай бұрын

I came here to say the same. Before becoming a ChemE, I solved problems like this using cross multiplication when I was studying for my technical level degree in Chem.

@shivanshukantprasad Ай бұрын

Calling veridical paradox a paradox itself feels like a veridical paradox.

@MachineCake Ай бұрын

I think one reason for the confusion by many people is because they (like I did initially) interpret the "water content" as a percentage of the VOLUME instead of the WEIGHT. I pictured watermelon-shaped containers 99% full of water changing to 98% full of water, which is a different problem. :P

@LLlAMnYP Ай бұрын

What changes if it's volume? Just like weight, the overall volume would reduce as well.

@lifeisajourney4340 Ай бұрын

@@LLlAMnYP Bro, What if it was 98% water, 1% Dry stuff, 1% Vacuum? Consider the watermelon is a closed system.

@LLlAMnYP Ай бұрын

@@lifeisajourney4340 > watermelon is a closed system Awww, hell no it ain't! XD

@lifeisajourney4340 Ай бұрын

@@LLlAMnYP What about the other question?

@RedFloyd469 Ай бұрын

@@LLlAMnYP if it's just a single percent drop in volume, there is no guarantee it would equate to 50kg, or 40kg or 37kg, or anything, because we don't know what the volume to weight ratio is. This was my problem too, and couldn't seem to solve the equation this way.

@marcusscience23 Ай бұрын

One way to think of it is that the percentage of dry weight goes from 1% to 2%, so it doubles. Along with the fact that the amount of dry weight remains constant, in order for the percentage to double, the total weight must halve, so the final weight is half of 100 kg, 50 kg. 50 = 100/((1-98%)*(1-99%))

@Stooge2 29 күн бұрын

That makes so much sense, thanks!

@jamesdlin7 10 күн бұрын

Yes, I think it's interesting that reformulating the question to be "the dry weight percentage increased from 1% to 2%" probably would produce much different results.

@M1412B Ай бұрын

In the Netherlands this problem was presented about 20 years ago on a national IQ test TV show as a stallholder selling 200kg of cucumbers on a hot day. I remember being stunned by the answer as it is so counter intuitive.

@ralanham76 Ай бұрын

For me the visual part makes sense if the dry weight was 2 yellow dots with 98 blue then " simplify" to 1 yellow and 49 blue.

@NotKnafo 2 күн бұрын

i remember this one but with potato they lose half of their mass because the 1kg solid content does not change and in order to get 2% solid from 1% you need to halve the water content

@TheLazyVideo 3 күн бұрын

The better way to think about it to use units that are invariable rather than units that are variable. Water content is variable, so let’s rephrase it into ruffage content (non-water content aka dry weight). The ruffage content was 1kg at the beginning. At the end, the ruffage content can’t be 2kg. The 2% ruffage means the total weight is 50kg, so the ruffage stays constant at 1kg.

@abhishankpaul 18 күн бұрын

IMO, this is more of a wording issue than mathematical

@ambhaiji Ай бұрын

0:10 I think an attempt was made to do the 'in the beninging' meme and then decide halfway to follow a civilized scientific discourse.

@melissascheid841 Ай бұрын

You forgot to ask the fundamental question, " What is the definition of water content / moisture content?" In soil mechanics, the definition of moisture content is the mass of the water divided by the mass off the solids. With this definition, you get very different results. This definition results in the mass of the solid to be 50.25 kg and the initial mass of the water to be 49.75 kg. The final mass of the water is 49.25 kg resulting in a final mass of the melon to be 99.50 kg.

@mab06 12 күн бұрын

Nonsense. You have inented an ambiguity that does not exist.

@ericaheathrow7085 16 күн бұрын

The shortest way to reason this is not to do any actual maths: use logic instead. Ask yourself not what has changed, but what *hasn't* changed; what hasn't changed is the amount of *hard* material. In the initial situation, 1Kg of hard material was 1% of the total. In the end, the same 1Kg is now 2% of the total; if 1Kg is 2%, then the total weight is 50Kg. (1 Kg hard material, 49Kg water) No actual serious math necessary, just quick logic. Going into algebra and variables and all of that is a very spoon-digging way of doing this, when using simple logic takes seconds.

@SpiritmanProductions 25 күн бұрын

I found it much easier to solve by looking at the dry weight, which doubled from 1% to 2% of the total, so, because no new dry weight could be added, the total must have halved.

@A-Negative Ай бұрын

I hated math, algebra, and calculus. Until you walked through this problem. Wow. I clearly had subpar teachers. Perhaps I would have stayed in the science field. Kudos.

@baze3541 Ай бұрын

I had the worst math teacher in high school and yet that did not hold me back from math or anything

@MarcoMagallanes-p2w Ай бұрын

@@baze3541Same my math teacher in highschool was so strict that everyday the test is different from what.we learned which yeh it's just so strict and evil She told us to advance in the book And she gave us a test that wasn't In the book and yeh I call her evil and strict

@jonahansen Ай бұрын

Yeah, well I loved science and math, but I often see arguments that make something so clear I realize my teachers were not all first class. The super-great teachers are few and far between, but could really improve the learning for students having a hard time. I suppose that is the mark of a good school, where the school recognizes and hires the best teachers.

@michaelsparks1571 Күн бұрын

Boss: WHERE DID HALF THE CARGO GO?!! Employee with watermelon stains everywhere: "Uh... you see um... water weight and uh..."

@p.g.8796 16 күн бұрын

The "problem" that I have with this, is the fact that we are looking at the final water percentage (98%) rather than what is lost from the original part (99% off 100). So in fact we are losing 1% of our starting point. The solution equation doesn't take that into account and is completely disconnected from the starting point. (And no, the 1kg is not the connection b/c it has no relative connection to the total balance). Imagine you have 99 yellow balls and 1 red ball. And after some picks you end up with 1% less yellow balls than you started with. How many balls are then there in total? It will most likely not be 50 balls. The problem is the re-phrasing of that task, saying after some picks I'll end up with a 1 red ball and an amount of yellow balls that will give me a 98% portion of yellow balls, over all balls.

@ListentoGallegos Ай бұрын

I love questions like these because they expose many people to the realization that their intuition is misleading.

@redplanetzeal1461 28 күн бұрын

To be fair, the question does not mention that the dry weight remains the same during the journey, so we can come up with any numbers for the answer, as long as the water content is 98%.

@JLvatron Ай бұрын

I got this right, but at 3:58 it is an assumption that the solid mass remained as this was never made clear in the question.

@camelopardalis84 Ай бұрын

@@JLvatron You are right. It is only implied.

@camelopardalis84 Ай бұрын

You are right. It was only implued, which is indeed not clear enough.

@bjorneriksson2404 Ай бұрын

Well, the "dry mass" can't exactly evaporate, so that mass remaining the same is an obvious deduction to make. Not everything should have to be "proven" in problems like this, because then you can start to demand proof of the fact that 50 is indeed half of 100 instead of just assuming that it is.

@TheEulerID Ай бұрын

Correct, and I have made the same observation, and it seems that, in addition to water, melons contain over 100 different volatile compounds.

@ModelLights Ай бұрын

@@bjorneriksson2404 ' "dry mass" can't exactly evaporate' Dry mass can't evaporate, and taking out 1% from the water weight doesn't make water magically drop to 50 kg from 99 kg. You guys realize at the 4:30 mark where the math is taking the ALREADY REDUCED TOTAL WEIGHT of 99 kg and multiplying it by '98%' which is NOT THE WATER REDUCTION FACTOR to get the 'paradox' is bad math, not a paradox, right? OF COURSE it reduced it too far, that 98% is self references 100%, not 'only the water weight reduction starting at 99%'. This is brain rot, I highly suspect the whole 'bunch of PhD's all arrived at this same answer after being told it was wrong' is completely made up garbage. If it was 100% water weight, and it reduced a percentage to 99% water weight, it would be 99 kg, it would NOT magically jump down to 50 kg from a 1% reduction. This is ONLY THROWN OFF A TINY BIT by 1 kg of the 100 being solid and not reducing by its 1% as well.

@cookesam6 29 күн бұрын

Man it makes you feel good when you get these right

@woodward4789 Ай бұрын

Imagine losing 50kg of water to summer heat. Those melons must be shrivelled messes

@justingolden21 23 күн бұрын

It's an ambiguous question. It can be interpreted as 98/99 * 100 or as 100 / (100-98)

@g.h.190 Ай бұрын

So many comments suggesting question is badly worded. To me it sounds like they are trying to invent an excuse for their failed answer.

@MaulikParmar210 Ай бұрын

English across world is pronounced and written differently, people will get it wrong even if relative grammar is correct. Comprehensive skills do not work when question is deliberately worded to create confusion and change meaning which could be expressed with more words. Welcome to languages 101.

@NichaelCramer 10 күн бұрын

I’m glad you included the final, more “visual” solution. It’ll help, for example, in “dinner-table discussions” where I might want to explain this interesting example to folks who aren’t interested in (or who might not follow) “all that algebra stuff”.

@verkuilb Ай бұрын

It becomes easier to visualize, if instead of saying “99%” and “98%”, you say “99/100ths” and “49/50ths”. Still challenging for many, but that difference in the denominator helps some people.

@abcd123906 11 күн бұрын

The most intuitive way to think about it is that, firstly, we know the dry weight must stay the same throughout. And yet, the percentage of the dry weight DOUBLED, from 1% to 2% of the total weight. So if the dry weight percentage DOUBLES while its absolute amount remains the same, the ONLY way that could happen is if the total weight HALVES.

@litcrit1624 Ай бұрын

I always did this one in my head. Originally the dry melon 1 kg was 1% of the whole; now that same 1 kg is 2% of the whole. So how much do you have to multiply that 2% to get up to 100%? 50. I have a feeling it would've been harder if the number is weren't so easy to keep in your head.

@yasseindahshan3556 Ай бұрын

I did this considering water contenet as moisture content which is (total mass of water/total mass of other) instead of (total mass of water/ total mass). Which made my answer ~=99.497487.

@simonliljeqvist Ай бұрын

Interesting to me is that removing more than half of the water (50/99) only decreases the water content by 1% units Edit: I meant concentration or ratio instead of content

@elSethro Ай бұрын

Looking at it the other way: "NOT water" has DOUBLED from 1% to 2%. This is a huge change. Since "NOT water" it is a constant (1kg both before and after), then water weight must have halved to produce that change.

@themyief2406 Ай бұрын

you are wrong here, the 99% was in terms of the starting weight but the 98% was in terms of the final weight.

@leif1075 Ай бұрын

@@themyief2406yeaisnt the accurate way to say it you reduced the water content by 1 percent. Yea that's right. Because it dropped from 99.percent to 98 oercent water..so it's loterally correct to say the water content dropped by 1 percent..not sure where he got 50/99 from.

@frankieking1941 Ай бұрын

Thank you for your coment, now I understand……..I think😅

@themyief2406 Ай бұрын

@@leif1075 Ok, I had a hard time understanding your comment as it has improper grammer, but I think what you meant by your comment was "It is alright to say that the water content dropped from 99% to 98%". But that would be incomplete, as it should be, "the water content dropped from 99% of starting weight to 98% of final weight". Edit: Also it is incorrect to say that the water content dropped by 1% as the basis of measurement (i-e starting weight and final weight) are not same.

@AUSinCH 40 минут бұрын

Hey Presh, there's a typo in one of your expressions. You mention that the dry weight (d) is 1% of the total weight, and you express this as: d=0.1(100)=1. The 0.1 should be 0.01, of course. Just mentioning this as some viewers might get confused by what they see on the screen.

@Catman_007 Ай бұрын

Simple solution.. Solid portion of watermelon will be constant. So Solid portion = Total weight x Solid portion % So we can say that total weight and solid portion % is inversely proportional to each other. As we can see percentage of solid portion changes from 1% to 2% So weight changes from 2 to 1.. Hence from 100 to 50

@JJOOOOSSSSSSSSHHHHHHHHHHHHHHHH 19 сағат бұрын

Logically, if it goes from 100kg to 50kg after dropping from 99% to 98% water weight, then at 97% water weight it will be 0kg, and starting from 96% water weight and lower, the watermelons will begin to have negative weight. If 96% water weight watermelons = 0 kg then that means 4% water weight = 100kg from the initial weight. Since 4% goes into 98% 24.5 times, we can determine that the correct final weight is 2,450kg at 98% water weight.

@tench745 3 күн бұрын

The thought that illustrated to me just how much weight it would lose is realizing that 50% water content would weigh only 2kg.

@ofofofff 17 күн бұрын

... we have 60% water in our body, if I loose at gym 1.65% from my 100kg, I will loose 50kg ? 😂😂😂 .. and if I loose 3.3% I can fly ?

@Keixxo Ай бұрын

When you first started explaining the answer, I was so irked, because I was sure that was wrong.

@BigNWide Ай бұрын

There is an assumption made in the answer that the 99% or 98% water is percent by *weight*; but it is also possible to interpret this part of the question as 99% or 98% by *volume*, in which case there is not enough information to solve the problem. Whenever you are given a percentage, the first question to be answered is "percent of *what*?"

@DhoklaAboveVadapav 26 күн бұрын

My boy Presh was blabbing for full 10 mins but your 4 liner comment made me understand in less than 30 secs. Thank you.

@Hs-wl3mn 24 күн бұрын

I have a barrel of water. The barrel itself weighs 1kg, the water in it weighs 99kg. The barrel is open at the top and 1% of the water has evaporated. Are you saying the barrel of water will weigh 50 kilograms?

@kankarych4642 13 күн бұрын

No. According to your interpretation, the barrel of water would weigh 99.01kg. However, the problem is formulated somewhat differently. It is not stated that 1% of the water evaporated, but rather that the percentage of water in the total volume decreased by 1, which significantly changes the situation. Let me try to explain using your example: Initially, in a barrel weighing 1kg, there were 99kg of water - this means that the ratio of water to the total mass was 99 to 100 or 99%. After 1% of the water evaporated(0.99kg), the ratio of water to the total mass became 98.01 to 99.01, or approximately 98.99%. In order to achieve 98% water content in the total volume for two masses differing by 1 kg (the weight of the barrel), it is necessary to take 49 as the mass of water. In this case, the total mass will be 50, and the ratio will be 49 to 50, which is the solution to the problem.

@Able89535 Ай бұрын

The terms “Absurd” or “counter-intuitive” are subjective, highly depends on your knowledge and your mindset (how you view the problem at first sight). Hence the term “Veridical paradox” is also subjective and some can think that it is, while others may think it’s not.

@furbyfubar 5 күн бұрын

It baffles how/why someone could think substituting watermelons with potatoes would make sense. What type of potato would have its water content be 99%? Google tells me that raw potatoes contain ~79% water, and cooking them only brings that number down. But because this riddle/paradox is mentioned so many times online, google suggest questions like "Are potatoes 99% water?" and then give the "suggested answer" from a page rephrasing this riddle.

@KaryoSentiko 2 күн бұрын

I'm a maths teacher, and I think the problem here is in the application. There has been a movement ( a good one in theory ) to teach maths in context as much as possible, as this makes it more engaging, easier to understand and more valuable. Hence a question about watermelons instead of just algebraic questions. But if you're going to write a contextualised question, you are signalling to the reader/solver that it makes sense in the real world. So they will expect the answer to be somewhere within the realms of predictability. If one were to guess, no maths involved, how much the watermelons would reduce, one might expect an answer in the realm of a few kilos, so their expectation would confirm the mathematically wrong answer. The mathematically correct answer here is absurd in real world terms. So, don't bother contextualising the question in the real world if it doesn't actually make any sense in the real world. This goes for any question like, "Little Johnny is trying to find the ratio of white flowers to yellow flowers in the meadow by his house" or whatever ridiculous scenario. There has never been a little johnny who wanted to work that out. This is not a real world example. Has never happened. Will never happen. Try harder or don't bother!

@ShawnF6FHellcat 20 күн бұрын

I got it right by using a weird version of the final method: You have 100 equally weighted units, where 99 are water and 1 is melon. The ratio is 99:1. Afterwards you have 98 units water and 2 units melon. This is a 98:2 ratio. In order to make the ratios compatible, I simplified 98:2 to 49:1. This means that there are a total of 49 + 1 aka 50 of the original 100 equally weighted units remaining. Since 1 unit was originality 1% of 100kg, we know that 1 unit = 1kg. Multiply 50 units by 1kg and you get 50kg final weight. This went much quicker and simpler in my head.

@BradHouser 5 күн бұрын

It is also interesting to note that if you want to dilute a liquid that is already 98% water, you would have to more than double (increase by 50/49) the water content to reach 99%.

@LaukkuPaukku Ай бұрын

At first the non-water weight is 1/100 (100%-99%=1%) of the total, then 1/50 (100%-98%=2%) of the total. Just multiply the non-water weight (which remains constant) by the inverse of the fraction to get the total.

@DonZauker1986 9 сағат бұрын

Non-water content has doubled from 1% to 2%. Therefore, total weight has halved from 100 to 50 kg. You don't need any equations if you know what you are doing.

@skwirlnone1543 39 секунд бұрын

its like figuring out humidity...

@yackawaytube 8 күн бұрын

It's called level-1 thinking vs level-2 thinking. Try this one. The combined price of 2 items is $1.10, first item is $1 more expensive than the second item, what are the prices of the 2 items. Level 1 thinking gives $1 and 10c, level 2 thinking gives $1.05 and 5c.

@IvanToshkov 23 күн бұрын

This is one of the reasons I'm always suspicious around percentages. They can be quite counter-intuitive. And the press *loves* to use them all the time.

@geoninja8971 Ай бұрын

Very cool. I started writing some equations, and soon worked out to convert everything to % of solids, then it all fell into place....

@CW91 Ай бұрын

After looking at your dots visualization at 9:10 actually, the answer is the watermelons stay the same weight. Because before the water was dried up, 99/100 water and 1/100 dry weight cannot be simplified anymore so that is the weight. But after the 1% water dried up, so we have 98/100 water which simplify to 49/50, and 2/100 dry weight is simplified to 1/50. Even though we have simplified the fraction to 49/50 + 1/50, this doesn't mean that the weight of the watermelon becomes 50kg. It simply means (49/50) * 100kg is water and (1/50) * 100kg is dry weight. So if we assume any water which is loss has been converted to dry weight, therefore there is no loss of weight at all. (If we assume that there is no conversion, then we need to know how much of the dry mass is left behind after the water decreased for that part of the fruit) This question is incomplete about mentioning how much does the dry weight actually weighs. ------------------------------------------------------- Ok after a little clearing up of confusion, I understand what the water and dry mass means. So water is only water without any sort of mass in it, which means that after it dried, there is no leftover mass for that part. And dry mass means that the fruit mass, which even includes those parts mixed in water. So now we know that 100kg of fruit with 99% of water and 1% of dry mass means that the 1kg of dry mass doesn't go anywhere. A completely dry fruit (after 100% water is dropped) still has 1kg of dry mass. So the calculations are correct as in the video: 98% water and 2% dry mass means that the 1kg is equal to 2%. Therefore 98% (which is 49 x 2%) is simply 49 * 1kg so it is 49 kg. The reason why the answer has an extreme drop of water mass is because the 1kg dry mass did not change in proportion to the 1% drop of water percentage. Thanks @jensraab2902 for clarifying😄

@jensraab2902 Ай бұрын

It doesn't say that 1% of the water dries up, it says that the water content drops to 98%. The assumption that this is the case when 1% of the water evaporates is the very thing Presh tries to demonstrate to be false.

@dirkbester9050 Ай бұрын

Evaporation to a gas does not "make the water dry mass".

@jensraab2902 Ай бұрын

@@dirkbester9050 I think you fundamentally misunderstand the problem. Nobody suggests that water converts into dry mass, that is ridiculous. When the problem says that the water content drops to 98%, it means that the water content decreases to such an extent that the dry mass, which remains unchanged!, now accounts for 2% of the watermelon. It is exactly this fact, which is that the dry mass does *not* change, that is the key to solving the problem. Previously, 1% of 100 kg was dry mass, i.e. 1 kg, with the other 99 kg being water. After water has evaporated (not converted!), the 1 kg is not 1% by 2% of the entire mass. For this to be the case, the entire mass needs to have decreased to 50 kg (because 1kg/50kg = 0.02). With 1 kg being dry mass, the remaining 49 kg is water. So 50 kg (99 kg - 49 kg) must have evaporated.

@CW91 Ай бұрын

@@jensraab2902 bro you are playing with words. Water does not dry up, but water drops, drops where? It is the same meaning of decreasing the water... Also 1/50 is simplified fraction of 2/100 which I have said 100kg is the original weight of the watermelon, so we cannot simplify it to 50kg... Anyway my last sentence in my comment is that we are not given information about dry mass, so this causes much confusion and uncertainty. Also imagine if the question says 100% of water decreased, does this mean that the fruit has no more weight? There is still dry mass remain after all water drops right?

@jensraab2902 Ай бұрын

@@CW91 I don't want to be rude (and hopefully will not sound rude) but there really is not uncertainty here. It seems to me that you, respectfully, somehow have difficulties decoding the wording of the mathematical problem (perhaps due to a language barrier?). It is of course the melon that dries up, not the water; it is the water _content_ that drops, not the water (it is the figure that drops, decreases, gets smaller, not physical water dropping like a drop of water). Anyway, you say that we don't have information about the dry mass but we do! I even made the quick calculation at the beginning of the third paragraph of my previous comment. The watermelons have a mass of 100 kg, right? We are told that 99% of these 100 kg is water (that's what 99% water content means). The other 1% is the dry mass. 1% of 100 kg is 1 kg. You ask what would happen if 100% of water decreased. "Does this mean that the fruit has no more weight?" - No, of course not. Unless the entire fruit consisted of water (which will not be true for any real fruit), there will be some rest left, the dry mass. "There is still dry mass remaining after all the water drops, right?" Yes, exactly. In the example at hand, this dry mass would remain at 1 kg. In fact, the dry mass of 1 kg never changes in our scenario, it is at 1 kg at all times. I hope this helped to clarify the situation a little! 🙂

@olmostgudinaf8100 24 күн бұрын

That is not a paradox. It's just a puzzle. A paradox is a puzzle that has two mutually exclusive solutions.

@Doeniz1 27 күн бұрын

I thought there was some trick involved and was pretty disappointed, when the solution turned out to be just the straight foreward approach.

@charlesbromberick4247 28 күн бұрын

I´d believe the economists blew it, but not the scientists. A scientist underatands percentages and would reason as follows: starting out we have 99kg of water and 1kg of solid (which won´t change). At the end 98% is water and this means 2% is solid (which is 1kg). So 1kg is 2% of total weight which implies total weight must be 50kg. Thanks for the fun puzzle, Presh.

@kamen42 3 күн бұрын

I am disappointed this needed a 10 minute video. This thing is so simple I was sure there is a second riddle after it.

@tomdekler9280 22 күн бұрын

I have no idea how watermelon water loss works so I got tripped up on the idea that the 1kg of "other weight" should remain the same. Maybe if it was clearer in the original question that the water evaporates instead of, idk, some chemical reaction that adds the hydrogen and oxygen atoms to the dry weight.

@CashueTM Ай бұрын

Question phrasing should say water content was 99% *** of its mass ***

@robertveith6383 Ай бұрын

No, it should state "of its mass."

@CashueTM Ай бұрын

@@robertveith6383yeah your right . I’ll edit the comment

@jensraab2902 Ай бұрын

Yes!!!! Full agreement. But in practice, I doubt that what is measured is mass. We usually measure weight and erroneously call it mass (or rather label the weight "kg" in error). I've never tried it but I suspect that if you weigh the same pack of, say, flour or sugar or whatever with ordinary scales at the poles or at the equator, the figure will be different but say "kg" when in reality it should be the weight in Newton. But then, the precision of these scales will probably not be good enough to measure that difference. Still, even though this is a math and not a physics puzzle, I think Presh should be more precise and use correct terminology. I'm sure he's aware of the difference.

@SmileyEmoji42 Ай бұрын

No. If it was %volume then it would be unsoivable because you'd have to know the density of watermelons. Any reasonable person, or anyone who's ever read almost any food ingredients label, will assume that it means % by weight (and only pedants will point to the distinction between weight and mass).

@jensraab2902 Ай бұрын

@@SmileyEmoji42 Did anybody talk about volume here? I don't think anyone did. As for the distinction between weight and mass, it may sound pedantic for ordinary people, but for folks with an affinity to physics (such as me) the difference is not at all trivial. I'm not Don Quixote, I won't be fighting against these windmills because I know it's a lost cause; I've accepted that in colloquial speech weight and mass is often used incorrectly. But in a place where people might not only be interested in math but also science, I think it's totally fine to remind people of the difference. People (and I don't exclude myself) sadly have so many misconceptions that there's no harm, in my opinion, to remind them from time to time of the actual facts. If nobody pointed out these misconceptions, how are any of us supposed to get rid of them?

@user-dq7vd1mf3j 2 күн бұрын

Math or grammar? By the math presented 90% water would mean that the final weight is 10kgs down from 100kg @ 99% water. Answers: 99% water = 100kg 98% water = 50kg 90% water = 10kg 50% water = 2kg Logically, 99kg - 2% = 97.02kg of water + 1kg of solids = 98.02k total weight. The logic error everyone has, understandably, is that something very heavy lost 1% of its heavy stuff, how much does it weigh now? But the end is a percentage of total weight which is a deceiving way to say something. A trick question. If you pose the it differently and say you have a 1kg container with 99kg of water in it. After some time 98% of the water remains. What’s the weight? Then you arrive at the answer most people get to quickly, 98.02kg.

@GetMeThere1 Ай бұрын

It's interesting that it would have been easier intuitively if you said the final percentage was 90%. One would say "well, if the dry weight was originally 1, and it's still 1, then the water would be 9, to make it 90%." And so it would weight 10 lbs. After a bit of head scratching, then, yeah, 10 lbs.

@yippee8570 Ай бұрын

10lb = 4.5kg, so nope

@delanomighty8113 20 күн бұрын

This is one of the first things we do as chemical engineers. The key is to do the calculations on the amount that does not change - i.e., the 'dry' mass.

@davidpardi3247 21 күн бұрын

Why does a drop of 1 percent in the water result in half the water being removed ?

@stophLINK 16 күн бұрын

Think of it as the dry weight doubling from 1 to 2 percent, but remaining at 1kg. So the total weight must be halved resulting in a large amount of water weight being lost. When I first encountered this (with potatoes instead of watermelon) all I could think of is how this must be one long train ride and that the potatoes would rot before losing that much moisture, and that it on a cellular level, losing moisture must be way more complex than it is in this brain teaser. But that it is exactly that, a brain teaser, and the laws of the real world don't apply.

@DerangedAussieMan 20 күн бұрын

The way I solved it was to look at the "dry weight". Watermelon is 1% dry weight and the total weight is 100kg. Now we get rid of some water so the dry weight is now 2% of the total weight. Since the dry weight doubled proportionally, then the total weight must've halved, so it must be 50kg now.

@0ur_6_stars 29 күн бұрын

So if water at last is *98%* , that means dry weight is *2%* . We know that dried weight is 1kg . Let the final weight be *w* . So , 2% of w = 1kg i.e., 2/100×w=1 W= 1×100\2 Which gives us *w=50kg*

@smthB4 29 күн бұрын

I think that this catches people out because they are used to percentage questions eg the number voting in a 2 party election where if a person stops voting for one party then they change to another party eg 1 votes blue 99 vote red, red is 99%, and you only need to change one red to blue for it to change to 98%. In this case, the water doesn’t turn into dry matter, it disappears completely, the equivalent in the red blue party example of red abstaining, in which case you would need 49 abstaining for the blue vote to rise to 2%, or 1/50

@kurzackd Ай бұрын

3:32 -- mate, *you're **_VERY_** WRONG ...* We are told in the riddle that the ratio of *volume of **_MATTER_* is 99 water to 1 fruit.... *NOT* that the ratio *OF WEIGHT* of water to fruit is 99 to 1... -_- Substances have different densities, you know ?? -_- *REAL ANSWER:* The watermelon has lost 1/99 of its weight during the trip. 1/99 of 100 kg is 1.01 kg. Therefore THE FINAL WEIGHT of the watermelons is ... 100 kg - 1.01 kg = 98.9898(repeat) kg... -_- *PERIOD.* .

@ExtraTrstl 5 күн бұрын

But if we don’t assume these ratios are weight, how are you getting an alternate answer? E.g.,, couldn’t the melon portion weigh 40kg, and the water portion weigh 60kg? If that’s the case wouldn’t your alternate answer be wrong?

@FreyGrimrod Ай бұрын

A PhD doesn't mean you are smart it means you are determined and willing to be hazed with trauma.

@harisimer Ай бұрын

No, a PhD shows a special aptitude for scientific work and research. If you are smart that very well might make a difference

@Kupferhans Ай бұрын

@@harisimer I think both cases exist. It would be ideal if everyone had a special aptitude for scientific work. But many people just want to have the degree because it helps them with their carreer and so they torture themself through it.

@yippee8570 Ай бұрын

Oh there's an American politician with a PhD who used the slogan 'Jesus, Babies and Guns' - I forget her name - and who believes the earth is flat and that we live in a 'globe conspiracy'. That might just be a reflection on American universities, I don't know...

@milanstevic8424 24 күн бұрын

In the end there is 2% (100% - 98% = 2%) of dry matter. Dry matter should still weigh exactly 1 kg (because it didn't evaporate) given by initial 100 kg * (100% - 99%) = 1 kg The weight where 2% would be exactly 1 kg is 50 kg because 50 kg * 2% = 1 kg (thus 1 / 2% = 50)

@stevethorpe 8 күн бұрын

I don't consider myself particularly good at maths, but my mind went straight to: "From the initial condition it is obvious that the non-water weight is 1kg. In the end that 1kg is 2% of the total weight, so the total weight must be 50kg. I guess that is similar to the 'dots' method, but without the dots 🙂

@Misteribel Ай бұрын

98% water + 1% ice + 1% other = 100%. Total weight 100kg. In a closed system, mass doesn't change. However, if you travel, weight will change depending on the location on the globe. Not enough info to answer the question.

@vclyel 14 сағат бұрын

if i have a piece of metal composed of iron and rust. it weighs 50kg and is 98% rust. i let it sit out to absorb more oxygen and water until it becomes 99% rust. how heavy is it now?

@knotwilg3596 25 күн бұрын

The fastest solution is focusing on the dry weight. At start it's 1%, by the end it's 2%. Its ratio has doubled, it's stable itself, hence the total weight has halved.

@anuragguptamr.i.i.t.2329 Ай бұрын

I am really very glad to see my Alma Mater's (IISc) one of the questions at this channel. 😍💥

@Prs722 4 күн бұрын

With the watermelon/potato problem, here's the way I visualize it. So it goes from 99% water by weight to 98% water by weight. This doesn't mean much so it's better to say it goes from 1% solids by weight to 2% solids by weight. The percentage doubles, but we don't magically end up twice as much solids, this means half the weight must have gone.

@nychold 3 күн бұрын

I did it a little differently. If the starting weight is 100kg and the water weight is 99% of that (99kg), the ratio is obviously 99(water)/100(total). If we lose water weight, we lose it from both measures, so (99-x)/(100-x) = 0.98. (99-x)/(100-x) = 0.98 99-x = 0.98(100-x) 99-x = 98-0.98x 1 = 0.02x 100 = 2x 50 = x

@bg6b7bft 19 күн бұрын

Mkay. I think it boils down to "there is always 1 kg of plant" 0.99 = water / (water + plant); solve for water, get 99kg of water and 100 kg total. 0.98 = water / (water + plant), solve for water, get 49kg of water and 50 kg total.

@devondevon4366 Ай бұрын

The water content is the percentage of the weight, which is water = weight of water / weight of water + solid) Hence, if the watermelon weighs 100kg and its water content is 99%, then the water weighs 99/100 or 100 kilograms = 99kg. Hence, the solid inside the watermelon weighs 1 kg (100 kg - 99 kg) Later on, the water content was 98% or 0.98. Since the weight of the solid inside the melon doesn't change (since it doesn't evaporate), then it will still weigh 1kg Hence, the percentage of weight, which is water = weight of water/ weight of water + solid Let the new weight of the water = n then 0.98 = n/ (n + 1kg) 0.98/1 = n / (n+ 1kg) 0.98 (n+1kg) = 1 *n cross multiply 0.98 n + 0.98kg = 1n 0.98kg = 1n- 0.98n 0.98kg = .02n 98 kg = 2n multiply both sides by 100 98kg /2 = n 49 kg = n So the new weight of the water = 49 kg since I set n as 'new weight of water' Since the weight of the solid (the red ) remained at 1 kg, then the new watermelon weight = 49 kg (weight of the water) + 1 kg (the red stuff we eat) = 50 kg

@metroid031993 Ай бұрын

The way I did this (and got the correct answer, knowing it was going to be tricky) was that initially, 1 kg was 1%. After the weight reduction, 1kg was now 2%. In order to get 100%, you need to multiply that 2% by 50, and since 2% is 1 kg, 1 kg * 50 == 50kg for 100%

@philliberatore4265 13 күн бұрын

From an engineering point of view, the dry weight (the meat) has a little effect on the total weight of the sample. It is mostly water, and the meat weight can be ignored. My approximation was half - 50 kg. Close enough.

@Peter_1986 Ай бұрын

I tend to be more of a visual learner when it comes to these kinds of puzzles, so the visual method at 9:15 made a lot of sense to me.

@RiiDii 6 күн бұрын

Got it. The fact that the riddle is asking for an answer that is a result of a change in ratio rather than a direct reduction is misleading if you're not paying attention. I have 10 stones of red and blue. If 90% of the stones are blue, and I only remove blue stones so that 80% of the stones are blue, how many stones are left? 5 = 1 red + 4 blue. The starting ratio of 90% means there is 1 red stone and 9 blue stones. The ending ratio of 80% means there is 1 red stone (didn't remove red stones) and 4 blue stones.

@SteBar3000 Ай бұрын

I put the question to Claude 3.5. Here's the answer This is indeed an interesting riddle! Let's break it down step by step: 1. Initially: - Total weight: 100 kg - Water content: 99% - Dry matter: 1% 2. Let's calculate the initial dry matter weight: - 1% of 100 kg = 1 kg of dry matter 3. At the destination: - Water content: 98% - Dry matter: 2% 4. The key point is that the dry matter weight doesn't change during the journey. 5. If 1 kg of dry matter is 2% of the final weight, we can calculate the final total weight: - Let x be the final weight - 1 kg = 2% of x - 1 = 0.02x - x = 1 / 0.02 = 50 kg Therefore, at the destination, the watermelons weigh 50 kg. This riddle illustrates an important concept: when water evaporates, the total weight decreases, but the proportion of dry matter increases. The absolute amount of dry matter remains constant, which allows us to calculate the final weight. Quite impressive, isn't it?

@andreketaren 29 күн бұрын

I checked the truck's cctv and saw some burglars stole half of the watermelons

@anilchandrapoudel3257 11 күн бұрын

Initially, Total mass=100kg watery% =99% Non watery mass =1%of 100kg =1kg Eventually Also non watery mass=1kg Total part=x kg(less than 100 kg obviously because of drying up of water) Watery%=98% Non watery mass=2%of total Total mass=non watery mass /2% X= 1/2%=50kg

@SushantKumar-yu2qi Ай бұрын

As I view it, if we, instead of focusing on water content, just equate the old dry mass(1kg) and that same mass present in 100-x kg of watermelon as 2% of it, it becomes clearer..

@yurenchu Ай бұрын

From the thumbnail: 50 kg. Due to the drying out, [99 kg water + 1 kg non-water] changes into [49 kg water + 1 kg non-water] , so the water content changes from 99% to 98% . 10 minutes of explanation? Okay, let's watch.

@Kitasia Ай бұрын

The question is confusing because you don't know what the 98% is referring to. 98% of the original whole or 98% based on the end ratio.

@wiggles7976 Ай бұрын

It means "98% water by mass." The total mass is M, and the mass of the water is W, and the mass of the watermelon rind is R. M = W + R, and 0.99M = W, and 0.01M = R.

@Kitasia Ай бұрын

@@wiggles7976 That formula works but, the interpretation opens a bit after dropping to 98% W = 0.99, R = 0.01 thus M = 1 Okay W/M = 0.99 (99%) Does the formula become W/M(initial) = 0.98 (98%) thus W = 0.98 R = 0.01 M(new) = 0.99 or W/M(new) = 0.98 (98%) thus W = 0.49 R = 0.01 M(new) = 0.5 It depends entirely on the frame of reference.

@andrasferencz7948 28 күн бұрын

I have solved it quickly with a method very similar to your latest solution. If 1kg dry part was 1% but becomes 2%, then 100% will be 50kg, which results 49kg of water. Q.e.d Talk to any finance guy (I'm an engineer, not a finance guy) about bond coupons and bond prices on secondary markets. Assume the prevailing interest rate is 1%. Someone issues a long term bond, with a $100 face value, and a 1% yield, which means that every year you will get a $1 coupon payment. Next year the inflation goes up, and the market will demand a 2% yield. What will be the price of the bond? Well, the bond will be traded for $50, because this way the $1 payment (the promised coupon) will mean a 2% yield, as demanded by the market. Obviously this will is a simplification (time to maturity, how sound is the issuer, and so on), but it is exactly the same idea.

@g.mitchell7110 Ай бұрын

I knew the answer right away, and not because I saw the same problem on Vsauce2 (The Potato Paradox). That video is about potatoes and this one is about watermelons. These are different types of food altogether.

@tolkienfan1972 Ай бұрын

Lol

@emurphy42 Ай бұрын

Sorry, I only know how to solve this for oranges.

@dirkbester9050 Ай бұрын

True, you can just plant the potatoes and hope for better luck next year. The watermelon in the picture are seedless, so no such luck.