I'm Officially Retarded

[Anonymous No.15169368]

I can't believe it, I cannot solve this simple math question. I came to the conclusion that it's ((9 / 4) + (6 / 3)) / 2 = 2.125 km/h, and then when I looked it up, my answer is actually wrong. Is it safe to say that I should kill myself as soon as possible?

Country - Percentage of Students who can solve this problem

Shanghai-China 31%
Singapore 19%
Chinese Taipei 18%
Hong Kong-China 12%
Korea 12%
Japan 8%
Macao-China 8%
Liechtenstein 7%
Switzerland 7%
Belgium 6%
Poland 5%
Germany 5%
New Zealand 5%
Netherlands 4%
Canada 4%
Australia 4%
Estonia 4%
Finland 4%
Vietnam 4%
Slovenia 3%
OECD average 3%
Austria 3%
Czech Republic 3%
France 3%
Slovak Republic 3%
United Kingdom 3%
Luxembourg 3%
Iceland 2%
United States 2%
Israel 2%
Ireland 2%
Italy 2%
Hungary 2%
Portugal 2%
Norway 2%
Denmark 2%
Croatia 2%
Sweden 2%
Latvia 2%
Russian Federation 2%
Lithuania 1%
Spain 1%
Turkey1%
Serbia 1%
Bulgaria 1%
Greece 1%
Romania 1%
United Arab Emirates 1%
Thailand 1%

source: https://www.oecd.org/pisa/test-2012/form/

[Anonymous No.15169389]

>>15169368
OP here, I finally found the answer myself, and I decided not to kill myself, it's (((60 / 9) * 4) + ((60 / 6) * 3)) / 2 = 28.33 km/h.

[Anonymous No.15169393]

>Percentage of Students who can solve this problem
where did you get those stats? they're not the same as reported from your link

[Anonymous No.15169414]

>>15169368
>I came to the conclusion that it's ((9 / 4) + (6 / 3)) / 2 = 2.125 km/h
you're leaving the denominators in minutes, the answer cannot possible have hours for the denominator without converstion

you also dont notice that one speed was 4km/9min and the other was 3km/6min, as you can see the fastest speed (the second one) "acted" for less time, so the average speed will be closer to the slowest speed

you also always should give an estimate to not make a gross mistake, the average cannot possibly be slower than the slowest speed or faster than the fastest speed

>Is it safe to say that I should kill myself as soon as possible?
Nah, just study Torah. There is a story about a student that needed to hear or read something 400 times before he understood it, compared to him you're fine.

>Israel 2%
That's a shame. It's probably the yeshiva kids who managed to do it

[Anonymous No.15169422]

I found another possible answer, add both the duration and the minutes and ot becomes 7 * (60 / 15) = 28 km/h. Why is the answer different than my previous answer? What's the difference and the correct ones here?

[Anonymous No.15169423]

>>15169389
you sure do seem to like talking about yourself, maybe you should continue to devote all of your time to talking about yourself on social media sites while ignoring on your studies completely.

[Anonymous No.15169424]

>>15169368
>Is it safe to say that I should kill myself as soon as possible?
It is. 7 kilometres in 15 minutes = 28 kilometres per hour. Most elementary school kids should be able to solve this in seconds.

[Anonymous No.15169436]

>>15169389
wrong, it's 28 (instead of finding the average of speeds, just add the distances and divide by the time). remember that the speeds are not acting for the same amount of time, so it's a "weighed average", which means you can't simply divide the speeds by two and get the true answer

to understand why that is you need to understand what an average actually is

>>15169414
>you're leaving the denominators in minutes, the answer cannot possible have hours for the denominator without converstion
i just realized OP inverted the distance for time too

[Anonymous No.15169442]

>>15169389
>>15169436
>>15169422
an average (more accurately, arithmetic mean), is the number you would get if all the amounts were distributed equally

what you're doing when you're finding an average is actually determining the lowest amount, then finding out what is difference between this lowest amount and all the other amounts. then you calculate the sum of all the "differences of the amounts" to then distribute it equally, getting you the average

in the problem, the lowest amount is the lowest speed, 4 km/ 9 min, the problem tells us this speed "acted" 9 times (9 minutes). so far we have

4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min

then, we have the fastest speed, which is 3 km / 6 min. the problem tells us this speed "acted" 6 times (6 minutes), so all the addends so far are

4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min
3/6 km/min 3/6 km/min 3/6 km/min
3/6 km/min 3/6 km/min 3/6 km/min

to find the average you need to distribute the sum of all differences. the difference of 3/6 and 4/9 is 1/18, which means our list of amounts looks like this

4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min
4/9 km/min 4/9 km/min 4/9 km/min
4/9 + 1/18 km/min 4/9 + 1/18 km/min 4/9 + 1/18 km/min
4/9 + 1/18 km/min 4/9 + 1/18 km/min 4/9 + 1/18 km/min

to get the average, that is, the equally distributed number, you need to distribute the sum of alll the differences. 1/18 is the difference and it happens 6 times as you can see, but there are 15 amounts you must distribute it too, so you must do (6 * 1/18) / 15 and add it to 4/9. In total you get 1/45 + 20/45, which is 21/45 km/min as the average

but remember, he wants the speed in km/h, so you need to convert it. 45 min is just 3/4 of an hour, so 21/45 km/min = 21/(3/4) km/h = 84/3 km/h which is equal to 28 km/h

hope you got everything, maths isn't supposed to be harder than it is

[Anonymous No.15169446]

>>15169393
>where did you get those stats? they're not the same as reported from your link
They are, you need to advance in the questions until you reach the one in op

[Anonymous No.15169447]

>>15169442

[Anonymous No.15169449]

>>15169368
Helen is faster than me, unless maybe she was pushing hard

[Anonymous No.15169450]

>>15169442
Thank you.

[Anonymous No.15169454]

>>15169368
It's average over intervals of time not to separate data points.
The answer is just (4 + 3)/(9 + 6).
Then times it by 60 to get km/h.
Answer is then 28km/h

[Anonymous No.15169455]

>>15169368
s=v*t
(3+4)=v*(9+6)
v=7/15 km/min = 28 km/h

What is even the point of public schooling?

[Anonymous No.15169456]

>>15159206

[Anonymous No.15169457]

>>15169368
Can /sci/ answer this one?

[Anonymous No.15169458]

>>15169450
don't mention it.

another exercise you can use to understand averages better is this

3 apples weight 5 kg and 7 oranges weigh 2 kg, what is the average weight of each fruit?

do this one with the formula you're used to, then try it by the method i explained (list all the quantities in terms of the lowest amount, find the differences, distribute the total sum of differences)

[Anonymous No.15169462]

>>15169458
>try it by the method i explained (list all the quantities in terms of the lowest amount, find the differences, distribute the total sum of differences)
What the actual fuck is this?

[Anonymous No.15169479]

>>15169462
Low-tier midwit intellectualism. They can't solve anything challenging so they will argue for hours about kindergarten problems and spew hot takes about their super-smart method of solving something that everyone already knows how to do with no though or effort.

[Anonymous No.15169487]

>>15169479
they also spam up the board with dozens of threads like this one, which should have been contained to the math general, its just more social media attention whoring, the flase premise of discussing math is just an excuse to justify every more social media dopamine addiction

[Anonymous No.15169491]

>>15169457
I'm assuming it starts in the very left configuration.
Per rotation 6 would be able to go through except for the first where only 4 could go through meaning 4 + 6*(3+4*29)
which is 718 people.

[Anonymous No.15169496]

>>15169479
>Low-tier midwit intellectualism. They can't solve anything challenging so they will argue for hours about kindergarten problems and spew hot takes about their super-smart method of solving something that everyone already knows how to do with no though or effort.
it's not supposed to be a "super-smart" method, it's about understanding what you're actually doing instead of just memorizing a formula and doing plug and chug.

the aversion for things like this (i.e. structural reasoning) is the reason people do very poorly in proof-heavy courses later in maths, because you actually need to understand what you're doing at each step of the proof if you want to get anything out of the course

>>15169462
>What the actual fuck is this?
it's the "common core approach" to the problem, which just means it seeks to make the person understand what a mean is so they don't do stupid mistakes later

>>15169462
>>15169479
>>15169487
then here is a problem for you gigabrains that like the thoughtless plug and chug method so much
>An old clattery auto is to drive a stretch of 2 miles, up and down a hill, /\. Because it is so old, it cannot drive the first mile— the ascent —faster than with an average speed of 15 miles per hour. Question: How fast does it have to drive the second mile— on going down, it can, of course, go faster—in order to obtain an average speed (for the whole distance) of 30 miles an hour?

[Anonymous No.15169498]

>>15169496
>it's about understanding what you're actually doing
What you're actually doing is trying to find a constant speed such that you would cover the same distance in the same amount of time. i.e. s=vt plug and chug. Nothing more to it. You are a midwit intellectual.

[Anonymous No.15169502]

>>15169496
45mph. Ez. Just do the calculation idiot

[Anonymous No.15169505]

>>15169491
>except for the first where only 4 could
How do you get 4? Does it start with 2 people already in it?

99.7 % of 8-year-olds in Hong Kong solved this correctly, by the way.

[Anonymous No.15169517]

>>15169502
great answer, it shows exactly the poitn i was making, school created a generation of entitled idiots

[Anonymous No.15169526]

>>15169517
>Entitled
I don't think you know what that word means. What, pray tell, do you think I feel I am entitled to?

[Anonymous No.15169531]

>>15169517
See >>15169498 and seethe harder, midwit "intellectual".

[Anonymous No.15169542]

>>15169442
Where did you get that 18 from

[Anonymous No.15169553]

>>15169368
>((9 / 4) + (6 / 3)) / 2
This is only taking the average speed among both routes but does not recognize the extra time it takes when traveling on the slower route. If you take 100 years to walk to the grocery store and make the return trip at light speed, it's not intuitive to say your average speed was ~1/2 light speed. Most of the time during the trip you were traveling veeeery slowly.
If another person traveled to the grocery store at 1/2 c, and returned at 1/2 c, their average is also 1/2 c.... but their round trip took much less time.

Therefore it's most intuitive to say the average speed is the entire distance traveled divided by the entire time spent traveling. That works out to 28 km/h as a few showed in this thread.

[Anonymous No.15169564]

>>15169553
>This is only taking the average speed among both routes but does not recognize the extra time it takes when traveling on the slower route
He doesn't need to recognize anything except the actual definition of "average speed", which isn't the average of the speeds, but the constant speed needed to cover the same total distance in the same total time. There's nothing to think about or recognize. It's a definition and the solution follows directly from it.

[Anonymous No.15169567]

The total is 7km.
It took her a total of 15 min.
So on total, the average, is 28 km/h. Because if she rode for an hour, which is 60 minutes, 4x15min, she would ride for 28km, 4x7km.

EZ

[Anonymous No.15169568]

>>15169542
1/18 you mean? 3/6 - 4/9 = 9/18 - 8/18 = 1/18

[Anonymous No.15169577]

>>>/pol/414443351
same spam being shilled on errrry board
>+28 replies and 5 images omitted. Click here to view.
cringe, way too many low iq npcs taking the bait for /sci/, why is this boards iq so fukkin low, what happened?

[Anonymous No.15169586]

>>15169568
You multiplied 3/6 by 3 and 4/9 by 2? I don't get why.

[Anonymous No.15169588]

>>15169568
>>15169586
Oh wait now I get it, you just made a subtraction between fractions. It's not really that intuitive when written in line

[Anonymous No.15169595]

>>15169414
>It's probably the yeshiva kids who managed to do it
no, it's academics. yeshiva students and the rest of the country are very weak in science fields and English as well.
t. israeli

[Anonymous No.15169619]

>>15169595
>no, it's academics
PISA isn't offered to academics, it's offered to middle schoolers (or high schoolers, I don't remember which)

[Anonymous No.15169639]

wow a bait thread on sci never thought someone would degrade so low as to make these

[Anonymous No.15169641]

>>15169619
I meant academics in a more ironic tone, people with a little understanding in math can solve this question, but these people make up a minority here.

[Anonymous No.15169670]

>>15169368
>>15169414
>>15169442
>>15169454
>>15169455
>>15169553
if you averaged the two average speeds of the two different paths instead of just considering the total distance and the total time it means you still have not intuitively understood the concept of an average speed and are relying on useless extra steps as a mental crutch

[Anonymous No.15169683]

>>15169577

[Anonymous No.15169691]

4 km / 9 min = 25.66.. kph
3 km / 6 min = 30 kph

Average can't be 2 kph, slower than walking pace

[Anonymous No.15169693]

>>15169670
> considering the total distance and the total time
Are you retarded? That's exactly what I did. Why are you linking to my post?

[Anonymous No.15169726]

>>15169368
It's OK to be wrong, OP. Posting here will teach you the opposite so I'd be careful listening to what anons say. You just forgot to multiply the result of 9 / 4 and 6 / 3 by 60, because 4km / 9m will give units in km/m.

[Anonymous No.15170415]

>>15169526
I meant arrogant, entitled is close but it isn't the same thing

[Anonymous No.15170681]

>>15169577
Bait for sure, but I'm just surprised how low those percentages are. Is the concept of an average that complicated? Do most students grasp them only by memorizing a formula or what?

[Anonymous No.15171092]

>>15169368
Is it zero?

[Anonymous No.15171117]

>>15171092
No, that's work

[Anonymous No.15171118]

>>15169368
>60/6*3 = 30
>60/9*4 = 26.67
>(30 - 26.67) / 2 = 1.67
>26.67 + 1.67 = 28.3 km/h
How fucked am I?

[Anonymous No.15171120]

>>15169458
>3 apples weight 5 kg and 7 oranges weigh 2 kg, what is the average weight of each fruit?
apples 5/3 = 1.67 kg (3.68 lbs)
thats some big apple energy right there
orange 2/7=tiny feminine orange energy

[Anonymous No.15171124]

>>15169442
>28 km/h
That's so much information just to get that answer.

9 + 6 = 15 minutes
15 / 60 = 0.25 hour
(4 + 3 = 7 kilometers) / 0.25 = 28 km/h

[Anonymous No.15171176]

>>15171124
>That's so much information just to get that answer.
i was trying to teach him, not give an answer

[Anonymous No.15172233]

>>15169577
the /pol/ version of this thread was way better

[Anonymous No.15172414]

>>15172233
so go back to pol

[Anonymous No.15174844]

>>15169496
>problem for you gigabrains
impossible because it went for 1/15 h for the first mile and has no time left to cover the whole distance in 2/30. But a proper plug and chug would yield the same because you'd get an infinite speed.
Mediocre teachers like you just cant make logical arguments short and snappy, so students are tortured with pages & huge blogposts explaining trivialities

[Anonymous No.15174858]

>>15171176
You're not teaching him anything remotely useful. You're just being a pseud and obfuscating the trivial essence of this probem.

[Anonymous No.15176544]

>>15174858
Diff guy. I would disagree. >>15169442 only has like 6-7 statements. I skimmed his answer and it seemed like it was teaching it right. I feel you only object to it because his response is "tall".
Getting kids to NOT put in the effort to read something in an ez 2-4 minutes, is def not the right way to teach kids at all. Hell, props to OP >>15169450 for even posting for help online. He wants to put in the effort.

Your answer >>15171124 is a good answer too, but only for some people. Some people catch on fast, but some people simply dont have a decent intuition of this stuff.
OP's error is that he considered BOTH paths to have EQUAL "weight".
>>15169442's answer is about the difference in "weight".
your answer >>15171124 is the correct way to do so, but doesn't really inform OP as to WHY to do what U did, which automatically includes "weight".

[Anonymous No.15176565]

>>15169368
>home and river 4km way
>rode from river to home in 3km
This problem requires use of the 4th spatial dimension?

[Anonymous No.15176644]

>>15176544
How is it intuition? It's probably defined in whatever textbook someone is used. Once you read that you know. If you get a question like this one you were probably told at some point that average speed is defined as distance travelled over the time taken. Then you just sum the distances, sum the times, divide and convert to the desired units. The only problem is people forgetting what they were told and not looking up things they don't know.

[Anonymous No.15177891]

>>15176565
>can't into 2 dimensions

[Anonymous No.15177920]

Helen returned from a river that was 4 km away by taking a 3 km route. Perhaps we should be asking how it is that Helen accomplished this feat because it appears that she travelled through a wormhole.

Anyway, the answer they want you to arrive at is 7 km / 15 minutes = 28km/h.

[Anonymous No.15177927]

>>15169368
Jesus Christ how are you so retarded just divide the total distance by the total time
holy shit