Easy math problem. I am having such a brain fart right now. Reddit Venn diagram r/askmath

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Easy math problem. I am having such a brain fart right now. Reddit Venn diagram r/askmath

Рет қаралды 16,328

5 ай бұрын

Here's a classic Venn diagram math problem: In a survey of 400 shoppers, 286 said that they did not purchase apples, 64 said that they purchased apples but not bananas, 80 said that they purchased apples but not cherries and 52 said that they only purchased apples. How many of the shoppers bought all three of the fruit?
This question is from Reddit r/askmath : / yh9srll1d6
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Пікірлер: 106

@bprpmathbasics 5 ай бұрын

In a college of 300 students every student reads 5 newspapers and every newspaper is read by 60 students. How many newspapers are there? (A) at least 30 (B) at most 20 (C) exactly 25

@bprpmathbasics 5 ай бұрын

Answer here kzfaq.info/get/bejne/mbWpjMqpyLnQYo0.htmlsi=tXX8yPppJtfIN3iw

@user-tz9ke5mo1q 5 ай бұрын

First comment plz listen

@user-tz9ke5mo1q 5 ай бұрын

Plz😊

@user-tz9ke5mo1q 5 ай бұрын

How to get this type of question

@highfall8145 5 ай бұрын

so if there are 300 students, each student reads 5 newspapers, and each newspaper is read by 60 students. so, if each newspaper is read by 60 students, then let there be x number of newsparpers . 1 student= 5 papers so 300 students = 1500 papers total . if 300 students read 1500 papers, and each newsparper is read by 60 students, x=1500/60=25 idk if im wrong bprp please repliy to my comment if it is correct or wrong

@cdkw8254 5 ай бұрын

Great videos man keep it up

@bergenxej6287 Ай бұрын

As a non native english speaker, the hard part is figuring wtf is the wording in this question

@lindenjenesse5078 Ай бұрын

As a *native* English speaker, the hard part is figuring out wtf is the wording in this question! 😆

@theriaa4580 5 ай бұрын

I never Knew that we can solve maths by this way Great video!

@bprpmathbasics 5 ай бұрын

Thanks!!

@ScottM1973 3 ай бұрын

That solution is sooo much more math than what I did. My Venn diagram looked the same but my A is no apples, B was no bananas, and C no cherries. Where there was no overlap the numbers were simply 286, 64, 80, and where B overlaps C but not A we have 52. So we have 400 - 286 - 64 - 80 however since the 52 is included in both 64 and 80 we need to add 52 back in 400 - 286 - 64 - 80 + 52 = 22

@TheTallRaver 5 ай бұрын

Great explanation👍👍

@bprpmathbasics 5 ай бұрын

Thanks!

@exhalerwolf1272 5 ай бұрын

Shopper A: I didn't buy apples Shopper A 20min later: I didn't buy apples but I bought bananas

@wobaguk 5 ай бұрын

Basically did it the same way, but labelled the 4 regions of apples w, x, y and z, and stated each part of the info as an equation, and it was a simple simultaneous equation to eliminate all but z. Maybe not better but better when you only have one colour pen!

@monkeywang9972 5 ай бұрын

That’s a much more advanced approach in American education systems. From my understanding folks in Europe learn maths through vectors and matrices, and if that’s the background would make sense to teach a beginner to approach this problem like that. I appreciated the approach for when my daughter is in 3rd grade and can show her like this.

@Brid727 5 ай бұрын

Do more videos on venn diagram please I suck at this and dont like it much but willingly do calculus 😅

@eriksyrnyk3528 3 ай бұрын

I got 22 by adding 64+80 for the a but not b/c, and then subtracting 52 from the total for the people who only bought a, and then subtracting the 286 for no a at all, since there could be many values for who bought a+b/no c, or a+c/no b, all that matters is finding the amount of people who didn't buy all 3

@Sg190th 5 ай бұрын

The 64 part I got lost but I'll re-watch and try to understand.

@Smellbo 5 ай бұрын

@Sg190th Basically, 64 people said they did not purchase Bananas, but that does not guarantee that they did purchase Cherries. Since we know how many people purchased ONLY Apples, we can remove them from the group (subtract them out), which would leave only the 12 people who bought both Apples and Cherries. Then, same logic for the people who bought Apples and Bananas, but not Cherries, and then again for the ones who bought all three. Hope this helped (:

@Sg190th 5 ай бұрын

@@Smellbo I think it did. I appreciate it!

@capnandy462 5 ай бұрын

It’s a very confusingly worded problem.

@agustinyornet4727 5 ай бұрын

Yup, somehow I got 22 too

@edwardblair4096 4 ай бұрын

But in the real world you often get different facts all jumbled together. Often the people collecting and reporting one fact have no relationship or knowledge of the people reporting another fact. Doing this kind of problem is all about figuring out how the various component facts are related to each other and whether they actually help you solve the question being asked.

@rugvedkulkarni1593 5 ай бұрын

Before watching the video: 286 people did not buy apples and therefore cannot have all the fruits. 400- 286 = 114 Of the 114 people who purchased apples 80 do not have cherries and 64 do not have bananas and therefore cannot have all three fruits. 80 + 64 =144 Of these 144 people in this group 52 of them brought only apples and thus would be counted twice in both not having bananas and not having cherries. This number of people is redundant therefore we subtract it. 144 - 52 = 92 All the other people who have apples and are not represented in this figure have all three fruits. 114 - 92 = 22 Therefore 22 people have all three fruits.

@rugvedkulkarni1593 5 ай бұрын

I did it :)

@bprpmathbasics 5 ай бұрын

Awesome!

@earl8295 5 ай бұрын

This question is fun.

@user-tz9ke5mo1q 5 ай бұрын

Plz i am crying

@alien3200 5 ай бұрын

Why bro😂

@gaelr.s7123 5 ай бұрын

Am crying saar

@kavinesh_the_legend 5 ай бұрын

🧻🧻🧻🧻🧻

@neclapiskin3017 5 ай бұрын

Hi, I have a problem also, could you help me please? Tom and Hugo take turns on duty at the hospital, with Tom every 12 days and Hugo every 10 days. They started their duties together on a Sunday. What will be the ordinal number of Tom's duty when they are both on duty together again on a Sunday for the first time after their initial duty? Thanks for your help.

@Kushina2404 5 ай бұрын

Would it be after 420 days because that is the lowest number divisible by 7, 10 and 12?

@Ridorim 5 ай бұрын

@@Kushina2404then divide that by 12 (Tom's interval) and +1 because start and finish both count.

@Issity 5 ай бұрын

This solution is only true if shoppers selected each option applying to them. So, only if f.ex. a person who bought only apples answered that they *only got apples* and *got apples but not cherries* and *got apples but not bananas*. Otherwise we would have 286 ppl with no apples + 64 ppl with no bananas + 80 ppl with no cherries - already >400 (and we didn't even add those 52 with just apples), so we know this underpaid intern can't even do a survey. I guess we're supposed to figure out that it must have been a multiple choice survey and everyone selected all options that apply, though I think this should be stated.

@marilynman 5 ай бұрын

Yeah, given that this sort or question is for basic computation you assume all aforementioned points. But in real life you just need to question how true the information is and make sure the people don't overlap with their answers.

@shafimuhammadkhaskheli6169 5 ай бұрын

I am from Pakistan love your teaching way

@bprpmathbasics 5 ай бұрын

Thanks!

@wdobni 5 ай бұрын

can you get the answer algebraically without using diagrams?

@lawrencejelsma8118 5 ай бұрын

Yes! It is called Boolean Algebra and Karnaugh maps math. You would define buying apples as A and not buying apples as "A bar or A with a bar hat" and the same thing for B (and B bar hat) and C (and C bar hat). You fill in the Karnaugh map as f(A,B,C) = permutations of A and A bar hat, B and B hat and C and C hat ... just like Karnaugh maps used for Boolean Algebra of 1s and 0s coursework. Your computer programming in machine languages courses in High School should have prepped you that of Boolean Algebra total studies (at least a little to know that base 10 in decimals is not the only counting systems).

@F1r1at 5 ай бұрын

Yeah, you just need to convert this task to some variables. Basically it's done in the video already, just shown in the form of diagrams for better understanding, I believe. Total count of people who bought apples is 400-286 = 114. So lets say that a = people who bought only apples, b = people who bought apples and bananas, c = people who bought apples and cherries, x = people who bought all 3 Then you have a system of equations: a + b + c + x = 114 a + b = 64 a + c = 80 a = 52 Then you just solve the equations: b = 64 - a = 64 - 52 = 12 c = 80 -a = 80 - 52 = 28 52 + 12 + 28 + x = 114 92 + x = 114 x = 114 - 92 = 22

@casusbelli9225 22 күн бұрын

@@lawrencejelsma8118It has nothing to do with Boolean Algrebra and K-maps.

@casusbelli9225 22 күн бұрын

Diagrams are just for easier representation. But basically, you have a set of all people who bought apples A (114) Two subsets of people that DIDN'T buy bananas/cherries (B and C, with |B| = 64 and |C| = 80 respectively) And intersection of those sets that has 52 elements. (B * C) You find the cardinality of the union of those two sets: |B| + |C| - |B*C| = 80 + 64 - 52 = 92. This is how many people bought apples, but didn't bought, at least, one or both of the other fruits. The 114 - 92 = 22 will be the number of people that bought those fruits.

@casusbelli9225 22 күн бұрын

The brain fart comes from poor wording that could be interpreted in a way that the three groups of people who bought apples would not overlap. Better wording would be: "286 said they didn't purchase apples. Out of the rest, 64 didn't purchase bananas, 80 didn't purchase cherries, and 52 purchased only apples)"

@lindenjenesse5078 Ай бұрын

OK, so not only is bprp great at math, he is also great at interpreting poorly used language!

@wisteria3032 5 ай бұрын

off the top of my head from 0 up to 34. now to see why I'm wrong edit: I was wrong because I forgot 12 people. 😂 I thought about them and then my brain said "oh, they're unimportant, who cares"

@vicheakeng4884 5 ай бұрын

Apples and carrots trading 0:30

@politicalfoolishness7491 5 ай бұрын

Ah, but if 286 said they did not purchase apples, what if some of the people surveyed did not purchase apples but didn't say for various reasons because let's be real and not imaginary. LOL FYI - the dad jokes are starting early today.🤣

@fahimuddin4401 5 ай бұрын

I thought the same.

@richardhole8429 5 ай бұрын

You have to use the information as given. No other info is needed and if stated, would be ignored.

@Sinsults 4 ай бұрын

The problem is that not enough information is given. Nothing in the problem says that all shoppers bought things. Half of that 286 could have bought nothing. All of that 286 could have bought nothing. All we really know is that somewhere between 80 and 114 people bought apples. That is not enough information to come to an accurate conclusion.

@ScottM1973 3 ай бұрын

My Venn diagram looked the same but my A is no apples, B was no bananas, and C no cherries. Where there was no overlap the numbers were simply 286, 64, 80, and where B overlaps C but not A we have 52. So we have 400 - 286 - 64 - 80 however since the 52 is included in both 64 and 80 we need to add 52 back in 400 - 286 - 64 - 80 + 52 = 22 Notice that where A, B, and C overlap that this represents the people who didn't but apples, nor cherries, nor bananas ie. bought nothing and we didn't actually need that to answer the question.

@areadenial2343 2 ай бұрын

Nothing about the problem changes if the 286 shoppers bought nothing. We're trying to find which shoppers bought *all three fruits,* but since these 286 did not purchase apples, they are immediately ruled out. We would do the same if they had purchased nothing. The rest of the problem involves similar deductions, and yes, there is enough information to determine which shoppers bought all three fruits.

@Sinsults 2 ай бұрын

@@areadenial2343 You can believe that if you want. I won't try to stop you. I will stand by what I said, regardless. Not enough information.

@Sinsults 2 ай бұрын

@@areadenial2343 and you can believe that all you want. I won't stop you. I still stand by my original assertion.

@Sinsults 2 ай бұрын

Okay AreaDenial. You can believe that all you want. I won't stop you. I still stand by my original assertion.

@zaidi3 5 ай бұрын

Assalamualaikum

@Sg190th 5 ай бұрын

Wa alaykum assalaam

@user-tz9ke5mo1q 5 ай бұрын

First comment sir plz listen me and talk plz reply fast i have watch your all videos plz reply and talk and help me

@user-tz9ke5mo1q 5 ай бұрын

Sir plz give me way to so I can also get this type of question plzz❤😢😢

@user-tz9ke5mo1q 5 ай бұрын

Plz talk until anybody else see

@whitelistedg 5 ай бұрын

LMAO WHAT IS THIS

@penguin9257 5 ай бұрын

What happened?

@lshan8981 5 ай бұрын

kya bol rha h bhai

@JubeiKibagamiFez 5 ай бұрын

0:28 (EDIT: The answer is 400. The question say specifically, "How many shoppers bought all three of THE FRUIT?", Not all three fruits. Again, all the numbers are a smoke screen to confuse us. The answer is 400.) My answer is either 0 or 400. If you subtract all the individual shoppers that didn't purchase all three fruits, you get less than zero customers. If you count all the customers as a collective, you get 400 customers buying all three fruits. I swear to God, I hate these so much.

@FufuZ 5 ай бұрын

I didnt watch the full video, but did you make sure to add only the specfic buyers like A only + B only + C only + A U B + ...?

@BigFellaDj 5 ай бұрын

the real life equivalent of the monkey clapping cymbals inside of homers brain

@kieragard 5 ай бұрын

Pretty sure by the way it's worded it's not all or nothing like you suggest. But a small fraction of the 400.

@agustinyornet4727 5 ай бұрын

The problem talks about a conjunction. Apples AND Bananas AND Cherries You need to buy all three of them to be considered as someone who bought all three of the fruit.

@JubeiKibagamiFez 5 ай бұрын

@@agustinyornet4727 I didn't get a chance to watch the whole video earlier. I will now.

@Sir.BlackHole 5 ай бұрын

1:38 NO. it says they did not purchased apple BUT WE HAVE NO IDEA IF THEY PURCHASED SOMETHING AT ALL! WHY YOU THNK THEY EVEN PURCHASED SOMETHING??? THE INFORMATION SAYS CLEARLY... THEY DIDN'T PURCHASED APPLE. BUT IT SAYS NOTHING ABOUT THE OTHER 2! it is like... 1000 people don't have a ferrari. 500 people haven't a car but they have a motorbike. 250 people don't have a motobike. You are saying that the 1000 People don't have a car???? they don't have THAT type of car not that they don't have any car! 2:40 NO! THEY SAID THEY HAVE PURCHASED THE APPLES NOT THE CHERRIES!!! THEY SAID THEY PURCHASED APPLES AND NOT BANANAS BUT WE HAVE NO IDEA IF THEY ACTUALLY PURCHASED CHERRIES, SO WHY YOU PUT THEM TOGETHER'?? DO YOU SEE THEY SAID THEY PURCHASED THE CHERRIES TOO??? I DON'T SEE IT. THEY NEVER SAID THEY PURCHASED SOMETHING ELSE-. 4:23 again... WE DON'T KNOW IF THEY PURCHASED THE BANANAS.... THEY COULD'VE PURCHASED THE BARRIES INSTEAD. why are you camping numbers and informations out your ass? Just follow what the text says! Do not invent informations from nowhere

@moistwatermelon3852 5 ай бұрын

Genuinely the most brain rotting comment I've ever read. Please tell me you're trolling.

@F_A_F123 5 ай бұрын

He doesn't say they purchased something. Everything in the square and outside of those 3 circles is people who didn't buy any of these things.

@kieragard 5 ай бұрын

Something tells me you're bad at math. If you don't like the real answer, go to a fantasy universe where your idea of math works.

@Sir.BlackHole 5 ай бұрын

@@kieragard i'm just realist. what if some of those 286 people never bought something? Stop assume shit.

@Sir.BlackHole 5 ай бұрын

@@moistwatermelon3852 why you you take it for granted that they bought the other fruit? they said they bought apples and not bananas but they never said they also bought cherries... it is like... 1000 people have a ferrari 500 people don't have a car but a motorbike 250 people have a car. how many people have the ferrari?? And why you assume only 1000 people have the ferrari? I NEVER SAID IF THE ONES WITH A CAR HAVE THE ACTUAL CAR MODEL OR NOT, SOME OF THEM COULD HAVE A FERRARI. stop assume shit from nowhere. and those 286 we don't know if they bought something at all BRUH! stop assume things from your ass. they could have purchased melons, tomatoes, meat, everything else, why do you assume things??? Be real. for example i'm one of those 286 who didn't bought apples BUT NOT EVEN CHERRIES OR BANANAS! what now???? clown

@Sir.BlackHole 5 ай бұрын

we don't have enough informations. 400 it's the total amount of people the store has right now. 286 people said they didn't purchased apples BUT we don't know if they purchased bananas or cherries. 64 people said they purchased apples but not bananas (we DON'T know if they purchased cherries) 80 poeple said they purchased apples but not cherries ( We DON'T know if they purchased bananas) and 52 people said they only purchased apples. (This is the only secure information we know lol) we need the total amont of person that purchased all 3 fruits, we have already 52 which is the only information clear. The limit is 400, 286 people didn't purchased apples but we have no idea if they purchased one of the other fruits, 64 and 80 did basically the same but with 1 fruit of difference. we can try with (52+80+64)/3 to find the average.... but the number would be 65,3333333 and i think it is strange so i will discard this option. we know that 64 and 80 have 1 thing in common.. both have purchased the apples but not one of the other 2 fruits... we can just use 52 + 80 + 64 for now since they all have this in common. to finding the rest of the fruit we can use 80/2 and 64/2 since they didn't buy one of the remaining 2 fruits but only 1. 80/2 = 40 64/2 = 32 Hypotetically only 32 people purchased 1 more fruit on those 64 and only 40 did the same. Now we have 40 + 32 and 52 + 80 + 64. we have now a total of 72 + 196 = 268 but if we add it to 286 we surpass by a lot the 400 limit... so this problem HAS NO SENSE TO EVEN EXIST. Cuz if we add up the ones who bought the apples only we get 196 then if we add it to 286 we get MORE THAN 400 which is the limit we have. THERE IS NO ANSWER TO THIS """"""""""""""""""""EASY"""""""""""""""""" MATH PROBLEM. WE HAVE NO INFORMATIONS ABOUT THE OTHER 2 FRUITS. ABSOLUTE NOTHING! WE HAVE ONLY THOSE 286 PEOPLE WHO DIDN'T PURCHASED APPLES BUT WE DON'T KNOW IF THEY PURCHASED SOMETHING AT ALL. If we have only x and not y and z, we can't do anything... we need atleast 2 of 3 informations to get the answer.

@cdkw8254 5 ай бұрын

I ain't reading all that... But the question is right though as far as I am aware.

@jinja3113 5 ай бұрын

From the information "64 people said they purchased apples but not bananas" you actually KNOW that they purchased cherries, because we already know 52 people ONLY purchased apples (As you said, it's secure information). So, 64 - 52 gives us the amount of people who purchased apples, but NOT ONLY apples, and also not bananas. Which is the same as saying people who purchased apples and other fruit distintc from bananas, that is apples and cherries. (64 - 52 = 12) You can deduce same for the 80 people. (80-52 = 28) From "286 people said they didn't purchased apples BUT we don't know if they purchased bananas or cherries", while it is true, is not the information we care about. The opossite of "286 people said they didn't purchased apples" is: "400-286 people said they did purchased apples" So we get 114 people purchased apples. Yes, we still don't know if they purchased other fruit, but we don't need that info. We already know that 52 bought only apples, 12 bought apples and cherries, 28 bought apples and bananas, all of these have in common apples: so 52 + 12 + 28 = 92 bought only apples or apples with only one other fruit. Which is the same as: 92 bought apples but did not buy all three at the same time. So finally 114 bought apples, so 144 - 92 = 22 bought apples, cherries and bananas.

@kieragard 5 ай бұрын

There is enough info. You're thinking all the purchases have to be confirmed to find all three purchases. It fact you don't need all the info and if you try to solve geometry there's a lot of info missing that you need to problem solve to get the answer.

@Sir.BlackHole 5 ай бұрын

@@jinja3113 why you you take it for granted that they bought the other fruit? they said they bought apples and not bananas but they never said they also bought cherries... it is like... 1000 people have a ferrari 500 people don't have a car but a motorbike 250 people have a car. how many people have the ferrari?? And why you assume only 1000 people have the ferrari? I NEVER SAID IF THE ONES WITH A CAR HAVE THE ACTUAL CAR MODEL OR NOT, SOME OF THEM COULD HAVE A FERRARI. stop assume shit from nowhere. and those 286 we don't know if they bought something at all BRUH! stop assume things from your ass. they could have purchased melons, tomatoes, meat, everything else, why do you assume things??? Be real. for example i'm one of those 286 who didn't bought apples BUT NOT EVEN CHERRIES OR BANANAS! what now???? clown

@quentind1924 5 ай бұрын

I already answered your other comment, but you are wrong. The problem do have a solution. And while we can't fill every box, we have enough information to solve the box "bought all 3 fruits", which is the only thing you have to answer First thing : 286 did not eat apples. So it's easy, only the 114 others are interesting and we don't care about those 286 that can't be in the "bought all 3 fruits" situation. So stop asking if they even bought anything, WE DON'T CARE ABOUT THEM Now, EXACTLY 52 people bought only apples. 64 did bought apples but not bananas, but exactly 52 of those only bought apples. Now question : where are the 12 others that are not in the "only apple" box while having no bananas ? They are in A, not in B, and they are not in the box "A, not B, not C", so the only box they can be is "A, not B, C".. Same logic with the 80 that bought apples but not cherries, and we conclude that 28 are in A, not in C and not in "A, not B, not C". So we know they are in "A, B, not C". Now, remember that 286 did not buy apples and there are 400 in total. Those 284 can't have bought all 3 fruits because they didn't bought apples (once again we don't care if they bought bananas or cherries). Same for the 54 that only bought apples, they therefore didn't bought all 3 fruits. Same for the 12 that only bought apples and cherries (that didn't bought bananas so they didn't bough all 3 fruits), and for the 28 that bought apples and bananas but not cheeries (so they didn't bought all 3 fruits). 284+54+12+28= exactly 378 that didn't bought all 3 fruits. But we know that there are in total 400 peoples. If exactly 378 are not in "A, B, C", that means that the 22 others must be in it and we have our solution