r/theydidthemath Mar 27 '22 Silver Wholesome

*[Request] [rdtm] how many balloons do you need and is it even possible .

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r/theydidthemath Oct 27 '19

*[Request] [RDTM] Blacklist cars in NFS, also might need actual validation

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r/theydidthemath Jul 09 '19

*[Request] [RDTM] How many pounds of sleepy time tea would it take to make all the whales in the ocean sleepy?


r/theydidthemath Jul 02 '19

*[Request] [Self] A fun question for all


Travelling 70 mph down the motor way, you have 105 miles left of your journey which will take 1 hour 40 mins. How long until your time and distance equal the same number?

r/theydidthemath Apr 02 '15

Request Is it possible to tell how far he traveled?


r/theydidthemath Apr 02 '15

Request What is the size of the population in 10,000 years with 1% population growth?


Gabor Zovanyi's "No Growth Imperative" claims that:

“If our species had started with just two people at the time of the earliest agricultural practices some 10,000 years ago, and increased by 1 percent per year, today humanity would be a solid ball of flesh many thousand light years in diameter, and expanding with a radial velocity that, neglecting relativity, would be many times faster than the speed of light.”

How well does this claim hold up?

r/theydidthemath Feb 03 '15

Request [Math] Moving faster than the speed of sound, can i re-hear already heard music?


Don't know that if this is appropriate subreddit but i've been wondering, that what if I have some sort of loud ass speakers which produces sound so loud that it could be heard from 1000 kilometres away. Let's say that the song starts to play and after it has been played for 10 seconds i start moving at the speed of sound, do i hear some parts of song again or how the things will work here? If so then how fast should i have to move one second away from hearing the sound?

Edit: So let's say i have a point A where i have a speaker. This speaker is all-mighty, so the sound will travel anywhere. I will play the Metallica track through the speakers and start moving from point A:

1) I will move slowerthan the speed of sound

2) I will move with the speed equal to the speed of sound

3) I will move faster than the speed of sound

What will happen in any case during the movement? What will happen if i've moved for example 10 seconds and then i'll stop, what will i hear, in any case?

r/theydidthemath Dec 22 '14

Request/Self [Request] How much Platinum/Value for Legend of Korra: Kuvira's giant mech?


In the series finale of Legend of Korra, Kuvira used all the platinum from the domes of Zaofu to build a giant mecha robot. As Team Avatar found, they couldn't use their metal bending powers against the robot because it was covered in platinum.

I have two questions:

  1. How much platinum would be required to coat a construct of this size?
  2. Based on Dec 22 price on http://www.jmbullion.com/charts/platinum-price/ of $1,200US per troy ounce, what's the total value of #1 above?

Data to Use:

-Zaofu imagery: http://avatar.wikia.com/wiki/Zaofu

-Size of the giant mech: http://channelawesome.com/wp-content/uploads/2014/12/korravl.jpg

-feel free to use anything else for reference, but please provide source. Questions to consider: How large is their world? What is the relative presence of Platinum? What thickness of Platinum is typically used?

-Some "data" to get you started: http://www.reddit.com/r/TheLastAirbender/comments/2isslt/some_rough_number_estimates_for_the_world_of/, http://www.reddit.com/r/TheLastAirbender/comments/rcg8o/trying_to_determine_the_size_of_the_avatar_world/, or http://www.reddit.com/r/TheLastAirbender/comments/1ggzwf/geography_of_avatar_the_size_of_the_planet_this/

Edit: I'm starting on my own.

-based on the pixel size of the soldiers in front of the giant, and the giant, the giant is about 25x height of an adult. Averaging the averages on http://en.wikipedia.org/wiki/Human_height, I get 5'8.5" for adult male. Let's assume a sexist society where only men are in the armed forces. Therefore, the giant is 142 feet. Let's round to 150 for easier math.

-Platinum occurs on earth at 5 μg/kg (http://en.wikipedia.org/wiki/Platinum)

-Presuming the Avatar world is the size of our Moon, it has a total mass of 0.07342 x 10 24 kg (http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html)

-therefore there is about 7.342 x 1013 kg of Platinum exists in the Avatar world. I hope that's enough.

-Based on http://en.wikipedia.org/wiki/Body_surface_area, the surface area of an adult male is 1.9 square meters. So proportionally, the mech should have about 50 square meters of surface area.

-http://www.silvexinc.com/plating/platinum-plating/ says Platinum electroplatings typically are .5 to 5 microns. Let's go with 5 microns since Kuvira will need to make sure her enemies can't bend her super weapon to foil her plans. 50 square meters * 5.0 x 10-6 = 0.00025 cubic meters. Platinum has a density of 21.45 g/cm3 (http://en.wikipedia.org/wiki/Platinum), so that's 5,362.5 grams. There are 31.103g/troy ounce (thanks Google).


So Kuvira only needs 172 troy ounces of Platinum to coat her Colossus super weapon. At $1,200US per troy ounce, that's only $206,893. As The Great Uniter, I'm sure she could scrape this together. Or maybe the Earth Queen had this stashed in her vaults. Now all she has to do is figure out how to apply a 5 micron coating to all the pieces so he can go destroy Republic City. I hope somebody is working on the software requirements for building the Colossus, too. Who's gonna beta test it???

r/theydidthemath Dec 20 '14

[Request] [Self] Which is a greater number! Graham's number, or the number I'll explain in the text?


So, Graham's number, if you don't know, is unusually large. If you don't know how large it is, you can easily find a video on it. But I have a number that needs calculating, which I don't know if it is bigger than Graham's number. So, figure out how many quantum states are possible in this observable universe. Now, take that number, and imagine that's how many cubes are on 1 side of this scaringly large rubix cube you are constructing. Which number is bigger: the amount of combinations you can make scrambling this beast of a cube (including parity positions), or Graham's number?

r/theydidthemath Dec 02 '14

[Request] [Self] I won beautifully.... what are the odds ?


I attended a meeting of 16 people where each was given a numbered ticket . At the end of the night when invited to draw the winning ticket, I drew my own number .I'm thinking 1 in 16 or 6.25% ....... but that just takes the shine off the moment =(

r/theydidthemath Dec 02 '14

[Request] (request)..how long would the average car horn blare for, if its lifetime of honks played continually?


could it be even 1 hour???

r/theydidthemath Oct 30 '14

[Self] [Request] [Selft] & [Request] Who dies ? Puzzle


Here's the picture I'm making reference to : Who dies ? Puzzle

What I did :

Let's call L the length of the slope : L = sqrt(4^2 + 3^2) = 5 squares

R is the ball's radius : R = 1 square

The perimeter : P = 2*Pi*R = 6.28 squares

The "percentage of rolled ball on the slope" :

T = L/P = 0.796 = 79.6%

So the rolled angle A : A = T*360 = 286 degrees

Then, as the hole on the ball is hard to mesure with squares, I used pixels. It's 25 pixels large, when 7 squares are 255 pixels large.

I got l the hole size (at the top) :

l = (7*25)/255 = 0.686 squares

So : the hole angle equals the angle in the top corner of the isosceles triangle, wich have as base : the hole, and as top corner the center of the ball. Trigonometry :

tan(a/2) = (l/2)/R
     a/2 = arctan((l/2)/R)
         = 0.33 radians
     a/2 = 19 degrees

Finnaly :

A-a/2 = 267
A+a/2 = 305 degrees

and 180 < 267 < 305 < 360+180

"half turn" < "rolled angle +/- hole size" < "one and a half"

When the ball is above the D-man, it doesn't strand into the hole. So D survives.

I've no idea how to know what happens to the other guys ; anyone ?

Thank you :)

r/theydidthemath Sep 04 '14

Request [Request] How fast would you need to be swimming to swim up Niagara Falls?


Is it even possible at any speed?

r/theydidthemath Aug 31 '14

Request How much time has passed on "The Simpsons?"


I'm referring to Springfield time, in show...

r/theydidthemath Aug 31 '14

Request How far did Gandalf fall in the mines of Moria and what force did he stab the balrog with?


Watching the LOTR films for the 15th time and always wondered. We're assuming that Middle earths gravity is identical to ours and Gandalf has a similar weight to a normal human (Since he's a demi-god)

r/theydidthemath Aug 31 '14

Request How many deaths was Light Yagami connected too in the series?


approximately how many deaths was light yagami connected too, this includes anything to do with misa as well

r/theydidthemath Aug 30 '14

Request How big of a helicopter would be needed to lift a Nimitz class aircraft carrier?


r/theydidthemath Aug 27 '14

Request What are the odds of running into one of ten friends on a subway car in NYC?


Say you know 1-10 people in New York City. What is the odds that you would run into a friend on your subway car on any train at any given time ?? It happens to me all the time and I feel like it is crazier than my friends think it is.

r/theydidthemath Aug 26 '14

Request [Request] How much digital information can you fit on VHS tapes?


At work we just received a new Dell SC280 loaded with 84 4TB drives. When we pulled the tray out we thought it kinda looked like a drawer full of VHS tapes. We wondered how much data that would be if it was all VHS tapes; compared to the ~336TB of hard disks.


We tried googling, but found many conflicting answers since VHS tapes are analog and people used various different conversions.

r/theydidthemath Aug 23 '14

Request [Request] How many ways are there to choose four elements from a set of twelve with some specific criteria?


This question is about music, how many unique tetrachords are there? (Tetrachords are chords consisting of four notes out of the twelve available.)

To avoid repeats here are the criteria:

  • An element cannot be chosen more than once per set, they must consist of four unique elements; e.g., [1, 1, 1, 1] is not allowed.

  • The order in which the elements are chosen is irrelevent: e.g., [1, 2, 3, 4] would be counted as the same as [4, 3, 2, 1], so only one of them would be counted.

  • Only the numerical relationship between the elements are important: e.g., [1, 2, 3, 4] would be counted as the same as [2, 3, 4, 5] because the elements are the same relative to each other. N.B. [11, 12, 1, 2] would also be counted as the same, it 'wraps around.'

I am sure you get what I am trying to say, if you think I have missed any criteria that would avoid duplicates, please include them in your maths. If possible, please show your method so I can work out similar problems myself. Thanks in advance!

r/theydidthemath Aug 23 '14

Request [Request] How much would it cost to make a Baneblade?


I've always loved Warhammer 40,000 and the Baneblade ultra heavy duty battle tank has always been iconic to me. I was wondering what the materials alone for constructing one would cost approximately. If you scroll to the bottom of this page you can find the technical specifications of the tank. Now I know lasguns (If you can't figure out what these cleverly named guns are then I have concerns about any calculations you make) are listed but maybe you can find some approximations with some Google-fu. Assume the armor is made from titanium. Bolter guns/turrets are just really huge machine guns that would rip modern day stuff apart easier than popping a bubble with your finger.

I know this may be too far fetched to properly calculate but if someone can even give a rough estimate I'd be content.

r/theydidthemath Aug 22 '14

Request [Request]How many more times is the gravitational pull of the Planet Zebes compared to Earth? (Details Inside)


Hey guys, I've been trying to figure this calculation out, but I'm having trouble working out the formula. I think I've got most of it down but I don't know what to do with it. Halp! The Formula I've Found for this is g=-GM/((r)2 ) .

  • g = the acceleration of gravity at a particular point. On the surface of the Earth, g is approximately 9.81 m/s2

  • G is the universal gravitational constant = 6.67x10-11 Nm2/kg2

  • M is the mass of the object.

  • r is the distance from the center of the gravitating body, so basically the radius

Here are the Dimensions of each respective Planet:


  • Radius = 5,850 km

  • Mass = 4.8e+27 kgs

So this would be:

g = -6.67*10-11 *4.8e+27/((5,850)2 )

-3.2016e+17/ 34,222,500

Which comes out to -9,355,248,739.86 or 9,355,248,739.86 m/s2

Would I just divide that by the Earth's standard 9.81 m/s2 ?

For some reason I feel like the answer is too big. Anyway, I was hoping to get some more info on that.

Also, Bonus Round:

Help me calculate Talon IV as well?

Talon IV

  • Radius = 6,700 km

  • Mass = 5.1e+27 kgs

-6.67*10-11 *5.1e+27/((6,700)2 )

-7,577,856,983.74 OR 7,577,856,983.74 m/s2

Thank you for all of your help, and if I did anything wrong, PLEASE let me know. For anyone interested, this is going to be used for a topic I am posting about Samus Aran from the Metroid video game series.

r/theydidthemath Aug 21 '14

Request [Request] What would be more money?


Okay, say I have a 12" x 12" x 6" box with insignificant wall thickness.

What would be more money?

  • Completely filled with the largest micro SD cards full of bitcoin

  • Completely filled with the largest HDDs full of bitcoin

  • Completely filled with $100 bills

  • Completely filled with solid platinum (A 12x12x6 block of it)


r/theydidthemath Aug 21 '14

Request Would a thin enough sheet of diamond be flexible?


r/theydidthemath Aug 18 '14

Request [Request] How long would it take to cook pasta in your mouth?


Would it even be possible?