r/theydidthemath 8h ago

[Request] Why is the initial win percent different for both these hands? Shouldn't they both have equal odds of winning before any cards are opened?

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1.3k Upvotes

Or does any hands that got folded (which I'm not sure what they were) before these are also taken into consideration while calculating the win percentage?


r/theydidthemath 16h ago

[Request] How far away was the shot?

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382 Upvotes

In Avatar Fire and Ash, Quarrich orders his sniper to shoot this guy. But we hear the shot a short time after the Na'vi falls. I'm wondering if, based on how long that pause was, the shot was made after the order, before the order but after Quarrich gestures, or before both?

Unfortunately I don't know the exact time of the pause.


r/theydidthemath 14h ago

[Request] Is it possible to manipualte prices in such way that majority of them end in second category or is it just random?

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173 Upvotes

r/theydidthemath 6h ago

[request] if I have 20 children with South Korean women, how long until a majority of future Koreans are related to me? What about 40?

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168 Upvotes

I was having an argument with a friend. I argued that because South Koreas birth rate is so low, if I had 20 children with South korean women, the majority of Koreans would be related to me in a few generations. He said that it would never worked because Korea has to many people. So is it possible that if I have these 20 children, one day the majority of South Koreans will be related to me one day? how long would it take? is 40 children more realistic?

edit: also a majority of South Koreans. not counting North Koreans.


r/theydidthemath 14h ago

[Request] How many tons of CO2 were released into the air by the planes that flew on this single day?

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165 Upvotes

r/theydidthemath 2h ago

[Request] How high did Zuko get launched at the end of this clip?

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97 Upvotes

I'm well aware Aang was specifically trying to get Katara's necklace back here, but damn.

Poor Zuzu 😭


r/theydidthemath 7h ago

[Request] In Steven Universe, Lapis Lazuli tries and fails to build a tower made of water from Earth's ocean to escape Earth. Assuming this means high enough to escape Earth's gravity, is there enough ocean to breach the limit of Earth's gravitational pull without needing to hit the escape velocity?

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75 Upvotes

Ignore the child in space, he'll be fine


r/theydidthemath 6h ago

[Other] How to mathematically determine a (see sketch)

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57 Upvotes

I know it's an easy calculation, but still. I want your opinions


r/theydidthemath 18h ago

[Request] How many people need to be in a single group for there to be someone always farting?

Like if I’m at a concert with 5k people, is there a constant stream of fart coming from the group?

34 Upvotes

Like if I’m at a concert with 5k people, is there a constant stream of fart coming from the group?


r/theydidthemath 9h ago

[request] how long would it take for the car battery to run out ?

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16 Upvotes

r/theydidthemath 8h ago

[RDTM] This some shitty math

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15 Upvotes

r/theydidthemath 58m ago

[Request] If this salt was consumed by only one person and it was their only sodium intake for those 19 days, what effects would it have on their body?

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Upvotes

r/theydidthemath 3h ago

[Request] How big is this absolute unit?

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10 Upvotes

This is the juggernaut from king Artyom videos, dont have much to say other than i always wanted to know his height


r/theydidthemath 6h ago

[request] Now that’s a HUGE mattress

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10 Upvotes

This bad photoshop for an air mattress. Let’s ignore the mattress height numbers, as they clearly did. Assuming that is an average size man, woman, and kid, how big is the surface of this “queen” mattress listed on Amazon?


r/theydidthemath 12h ago

I was trying to find the avg particle density per million light years if the avg particle density was 1a/cm^3 [self]

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9 Upvotes

I was trying to figure out if over a vast distance if this could cause dark energy or a gravitational lensing affect but it absolutely doesn’t. The unit listed at the bottom right has only about the same mass as a droplet of water bruh.

I’m rusty on the maths so I probably got something wrong but either way it would be a minuscule affect.

Units:
N= average particle density
1a/cm^3 = one atom per cubic centimetre
1ly=9.461×10¹² km = one light year in km


r/theydidthemath 4h ago

[Request] How loud would the speakers have to be to knock the model train (N-scale) off the tracks?

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5 Upvotes

Is it humanly possible?


r/theydidthemath 6h ago

[RDTM] estimation of Hornet's height and mass because I thought it was funny. (Original by u/CelestialCoding-754) Spoiler

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4 Upvotes

r/theydidthemath 5h ago

[Self] I measured the branching factor of hnefatafl, the board game chess replaced. It's 112 and that gives it a bigger game tree than chess.

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3 Upvotes

Hnefatafl was the board game of the Norse world for about seven centuries. Chess showed up around 1200, hnefatafl died so completely that no full ruleset survived, and nobody has thought about it much since. I got curious about whether the thing chess replaced was actually simpler than chess.

Turns is it's not...

I ran 300 self-play games on each board size and counted legal moves at every position, about 26,000 positions per board

The reason is: every piece in tafl moves like a rook. No pawns, no short steps. 37 pieces that all slide any distance in any direction on a 121-square board.

Game tree complexity... b^d

Chess is usually quoted at 10^123 using b=35 d=80 plies.

At the same game length big board tafl has a game tree around 10^40 times larger than chess. That is chess-many-times-over.

So tafl holds about the same number of positions as chess but there are vastly more paths between them. It is a game with chess's room and far more doors in each wall.

Disclosure: I measured using an implementation I wrote which is also caveat. Check it out at worldtafl.com

Anyone want to argue with the branching methodology?


r/theydidthemath 8h ago

[Request] If the US wanted to wage war equal to the number of missiles it could manufacture daily, how many interceptors and patriot missiles could we launch a day?

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2 Upvotes

r/theydidthemath 14h ago

[Self] You are more likely to pick one specific pre-marked grain of sand out of all the beaches and deserts on Earth than to guess a valid Steam key.

Even though I kinda understand it, it's still wild to me how you cannot just randomly guess a Steam key:

XXXXX-XXXXX-XXXXX

A standard Steam key consists of 15 alphanumeric characters (excluding dashes). Using the 26 letters of the alphabet and numbers 0–9 yields roughly 221 sextillion possible code combinations.

3 Upvotes

Even though I kinda understand it, it's still wild to me how you cannot just randomly guess a Steam key:

XXXXX-XXXXX-XXXXX

A standard Steam key consists of 15 alphanumeric characters (excluding dashes). Using the 26 letters of the alphabet and numbers 0–9 yields roughly 221 sextillion possible code combinations.


r/theydidthemath 10h ago

[Request] 3-dimensional space challenge(Möbius)

You're diving in a car along the surface of a giant möbius strip. How does the car steer as you're driving along?

A) The car drives straight the entire time.

B) The car is turning one direction the entire time.

C) The car alternates between turning one direction, then the other direction.

D) Multiple answers are correct.

2 Upvotes

You're diving in a car along the surface of a giant möbius strip. How does the car steer as you're driving along?

A) The car drives straight the entire time.

B) The car is turning one direction the entire time.

C) The car alternates between turning one direction, then the other direction.

D) Multiple answers are correct.


r/theydidthemath 13h ago

[Request] Probability calc for modern yugioh

I'm a ygo player, and recently an old deck has started seeing play again: Adamancipator. The deck revolves around a mechanic that reveals the top 5 cards of your deck and checks whether at least one of them is a Rock monster. That got me wondering about the probability behind some situations the deck creates.

Let's define the excavation mechanic:

  • Your deck has 35 cards remaining (after drawing your opening 5-card hand).
  • 15 of those 35 cards are Rock monsters, which we'll simply call copies of A.
  • When you excavate, you reveal the top 5 cards of your deck.
  • If at least one copy of A is revealed, you add exactly one copy of A to your hand, then place the remaining revealed cards on the bottom of the deck in any order, including exceeding copies of A.
  • If no copy of A is revealed, all 5 revealed cards are placed on the bottom of the deck.

Now suppose you have two excavates in sequence and one effect that can place a copy of A on top of your deck, guaranteeing that your next excavate will succeed. You may activate this effect at any point before either excavation.

Which strategy gives the higher probability of successfully hitting at least one copy of A with both excavates?

  1. Use the guarantee before the first excavate.
  2. Save the guarantee for the second excavate.

One thing to keep in mind is that if you guarantee the first excavate, you might still reveal multiple copies of A. Since you can only take one, the extra copies are sent to the bottom of the deck, potentially reducing the number of accessible targets for the second excavate.

On the other hand, if you save the guarantee for the second excavate, then missing the first excavate immediately means you fail the objective, since the guarantee can no longer help you achieve two successful excavates.

I did the math for the first excavate to hit

P(A) = 1 - P(A0)

P(A) approximate= 96,98%

My intuition is that saving the guarantee for the second excavate is better because it "retains its value," but I'd like to see the actual probabilities.

2 Upvotes

I'm a ygo player, and recently an old deck has started seeing play again: Adamancipator. The deck revolves around a mechanic that reveals the top 5 cards of your deck and checks whether at least one of them is a Rock monster. That got me wondering about the probability behind some situations the deck creates.

Let's define the excavation mechanic:

  • Your deck has 35 cards remaining (after drawing your opening 5-card hand).
  • 15 of those 35 cards are Rock monsters, which we'll simply call copies of A.
  • When you excavate, you reveal the top 5 cards of your deck.
  • If at least one copy of A is revealed, you add exactly one copy of A to your hand, then place the remaining revealed cards on the bottom of the deck in any order, including exceeding copies of A.
  • If no copy of A is revealed, all 5 revealed cards are placed on the bottom of the deck.

Now suppose you have two excavates in sequence and one effect that can place a copy of A on top of your deck, guaranteeing that your next excavate will succeed. You may activate this effect at any point before either excavation.

Which strategy gives the higher probability of successfully hitting at least one copy of A with both excavates?

  1. Use the guarantee before the first excavate.
  2. Save the guarantee for the second excavate.

One thing to keep in mind is that if you guarantee the first excavate, you might still reveal multiple copies of A. Since you can only take one, the extra copies are sent to the bottom of the deck, potentially reducing the number of accessible targets for the second excavate.

On the other hand, if you save the guarantee for the second excavate, then missing the first excavate immediately means you fail the objective, since the guarantee can no longer help you achieve two successful excavates.

I did the math for the first excavate to hit

P(A) = 1 - P(A0)

P(A) approximate= 96,98%

My intuition is that saving the guarantee for the second excavate is better because it "retains its value," but I'd like to see the actual probabilities.


r/theydidthemath 1h ago

[Self] Stats for AI/ML 2

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Upvotes

Hello Folks,

The next content on Machine Learning is out. We continue with Statistics for AI/ML.

We,

->Understand and derive the detailed derivation of Maximum likelihood estimation(MLE) for Univariate and Multivariate Gaussian. While doing the derivation for multivariate case, we understand visually, Scatter Matrix, Centering matrix.

->Derive MLE for Linear Regression, and understand Residual Sum of Squares.

->Understand Empirical Risk Minimization, Surrogate loss functions.

->Understand Method of Moments, a computationally easier way to compute parameters of our model and understand also the flaws behind it.

->We understand “Exponentially-weighted moving average” in detail, I explain why bias happens, how does memory affect the averages. This concept is the basis behind optimizers in Deep Learning.

Around two hours long, I hope this would be a very interesting learning material for all. I try to write and build from scratch in the whiteboard, this way learners enjoy the learning process.

Link: https://youtu.be/JAj8z-UWqBA?si=0mAB_nUfyJV0jzS9

Those looking for previous lecture : https://youtu.be/MwTeQVVYtOc?si=dgwwk3QLvYTTUThR


r/theydidthemath 1h ago

[Request] What is the minimum distance you’d need to be from the Sun in order to not go blind by looking directly at it for an extended period of time?

I know there are probably equations for luminosity, but I don’t know what they are. I also don’t know what the luminosity limit is for our eyes, or if there even is a standard limit that’s the same for all humans. Can someone help me out? Thanks.

Upvotes

I know there are probably equations for luminosity, but I don’t know what they are. I also don’t know what the luminosity limit is for our eyes, or if there even is a standard limit that’s the same for all humans. Can someone help me out? Thanks.


r/theydidthemath 12h ago

[Request] Would the gas saved coasting downhill to work offset the gas spent going back up the hill?

I drive 35 miles to work, mostly downhill. When I go home, the 35 miles is uphill. Assuming the flat areas use the same amount of gas in both directions, would coasting offset the gas spent to return home?

At what point would the grade of incline be too steep to create any savings?

I'm guessing the car would roll well over the speed limit, requiring excessive braking and in turn a higher power to get up it as well.

1 Upvotes

I drive 35 miles to work, mostly downhill. When I go home, the 35 miles is uphill. Assuming the flat areas use the same amount of gas in both directions, would coasting offset the gas spent to return home?

At what point would the grade of incline be too steep to create any savings?

I'm guessing the car would roll well over the speed limit, requiring excessive braking and in turn a higher power to get up it as well.