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Mordhaus (Member Profile)

ant (Member Profile)

ant (Member Profile)

Secrets to measuring a piece of paper - Numberphile

siftbot says...

Tags for this video have been changed from 'secret, measure, numberphile, cliff stoll, lesson' to 'secret, measure, numberphile, cliff stoll, lesson, clifford stoll' - edited by notarobot

Mordhaus (Member Profile)

YouTube's Rules Don't Apply to Everyone

ChaosEngine says...

Youtube are consistently inconsistent. As much as I admire some youtubers and think making short films would be a great way to make a living, I am so glad my income is not dependent on the increasingly arbitrary whims of google.

For example, Brady Haran of Numberphile made a video about "derangements", a concept in combinatorial mathematics. Fairly dry stuff unless you're a math geek. YouTube flagged the video and even when he submitted it for "manual review" it was still deemed inappropriate for advertisers.....

although the problem has apparently since been resolved. Nothing to do with Brady also having an immensely popular podcast where he complained about it, I'm sure. (For the record, Hello Internet is awesome!)

4 Revolutionary Riddles

ChaosEngine says...

This line is incorrect Vavg = (V1+V2)/2. That only applies if you run at V1 and V2 FOR THE SAME AMOUNT OF TIME.

Speed is Distance divided by Time, so the formula for calculating average speed is Dtotal / Ttotal.

The problem is that that only works if your second lap can be longer than the first lap.

If they are the same distance, the maths are undefined.

V1 = D1/T1
V2 = D2/T2

Vavg = (D1+D2)/(T1+T2)
if (D1 = D2) then
Vavg = 2D1/(T1+T2)

if Vavg = 2V1 then
2D1/T1 = 2D1/(T1+T2)
then T2 = 0

therefore V2 = D1/0 .... cannot divide by 0 (and no, it's not infinity )

Digitalfiend said:

The track question seems really straightforward. The question is how fast do you have to run the 2nd lap such that the average of the two laps (Vavg) is twice the velocity of the 1st lap (2V1); so Vavg = 2V1 (says right in the video). Unless I'm missing something, V2 has to equal 3V1:

Since the problem states that Vavg must be 2V1, we can substitute that in the average calculation below:

So, Vavg = (V1+V2)/2 becomes 2V1 = (V1+V2)/2

Now solve for V2:

V2 = 4V1-V1
of
V2 = 3V1

i.e. your 2nd lap must always be 3x faster than your 1st lap so that the average of the two laps is twice the velocity of the 1st lap.

No?

For example:

V1 = 1 m/s
V2 = 3 m/s
Vavg = 2 m/s

2m/s = 2V1

V1 = 5m/s
V2 = 15m/s
Vavg = 10m/s or 2V1.

Why is it Hot Underground

brycewi19 (Member Profile)

Siri, What Is Zero Divided By Zero?

modulous says...

http://videosift.com/video/Numberphile-Problems-with-the-Number-Zero

Skip to 10 minutes for 0/0 if you don't want the background. A quick spoiler clue is that x/x = 1; Also, 0 x 0 = 0, which implies the answer is 0. Indeed, there are a number of different mathematical constructs one can make to demonstrate that the answer is any number one likes.

Mathematics needs to be uniform and consistent, and an operation that can return infinite legitimate values depending on your approach is a disaster as far as this is concerned. Suddenly the whole enterprise of mathematics is ruined. Better to call 0/0 undefined.

Into English and cookies. How many cookies does nobody get when you don't divide cookies among no people? Does this make sense?

Into speed. If I am travelling at speed and you want to measure it you need distance travelled and time taken. If I travelled 100 kilometres in 1 hour you can say I'm travelling 100kph. If I travelled 50 kilometres in half an hour (50 / 0.5) , you can say the same thing. 25km in quarter of an hour (25 / 0.25) and so on and so forth. All come out at 100kph. But what if you decide to measure how far I travel in 0 seconds? I travel 0 metres. 0 / 0 = ? 0kph? And if you took this narrowly focussed measurement every few seconds you would see that my speed remains at 0kph but I manage to cover 100km in an hour anyway. Maths is now broke

iaui said:

I understand why for n > 0 n/0 is indeterminate but I'm not convinced 0/0 isn't simply 0. If you have zero cookies and split them amongst zero friends then nobody gets anything so zero?

The Imitation Game - Official Trailer

ChaosEngine says...

So Tywin Lannister hires Sherlock Holmes to defeat nazis??? Sold!

this actually looks good. If anyone is interested, there's a good video on the enigma machine on the sift.
*related=http://videosift.com/video/Numberphile-The-Fatal-Flaw-of-the-Enigma-Code-Machine

The Imitation Game - Official Trailer

Why Does 1% of History Have 99% of the Wealth?

Drachen_Jager says...

First off, I don't think those base numbers are accurate.

But even if they were, looking at averages doesn't make any sense.

The average wage of 100 people earning $10 a day is $10 a day.

The average wage of 100 people where 99 earn $1 a day and 1 earns $901 a day is $10 a day.

Talking about averages is a good way to confuse people when what should be discussed is the median number (for those non-numberphiles, the median is the point where half the group is above that number and half is below).

skytyping pi in the sky

What your phone’s buttons layout could have looked like



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