/r/theydidthemath

And they said math has no real world applications

Proper title tags are

**required**for all posts or it will be**removed!**The tags accepted are at the end of the sidebar down there.State clearly what is being or what you want calculated in the title. [Request] posts must have a calculable answer; otherwise, they will be removed.

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For easy and quick math results (ex. How many feet are in a mile?) use Wolfram|Alpha™. Posts containing "simple math" will be removed, as well as requests whose answers are easily searchable online, and any other post at the moderators' discretion. For more abstract math, try /r/math or /r/learnmath.

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`[; e^{\pi i} + 1 = 0 ;]`

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**[Request]**- Asking the /r/theydidthemath community to do the math for you!**[Self]**- You did the math and want to share it!**[RDTM]**- "Reddit Did The Math", linking to a comment or post on Reddit where someone else does the math!**[Off-Site]**- Use when linking to any site, including Imgur, that is**not**reddit.com.**[Meta]**- Non-math posts regarding the subreddit itself. Don't use this unless you really have to.

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/r/theydidthemath

1

Would this mean I have a 75% chance to win?

I was speaking hypothetical with my boss today about odds. I asked if he knew there was a raffle of 100 tickets, 25 were sold would you buy the remaining 75 and take that 75% chance of winning. He explained that it wasn’t actually 75%. Could someone explain what it would actually be in terms of %?

2 Comments

2023/11/30

23:25 UTC

23:25 UTC

1

In a game I am playing I've come across a problem that essentially boils down to the title. I'd like to learn how to calculate this probability

2 Comments

2023/11/30

23:10 UTC

23:10 UTC

0

5 Comments

2023/11/30

23:05 UTC

23:05 UTC

1

I will post a link in the comments to the video explaining the trick, but I did it myself once and it did work. I’ll try to explain in words as succinctly as possible.

First, randomly shuffle a deck of 52 playing cards. Flip the top card over, and note the value of the card. Next, add a number of cards to continue counting up from the value of the top card to get to “king,” (13). For example, if the top flipped card is a 9, you would flip 4 cards—10, J, Q, K. Set that whole pile of cards flipped face down, aside.
Repeat this process 4 times to result in 5 piles of cards. **He does not mention what to do with an Ace in this trick, but I wound up with one and counted it as a value of 1**
Randomly choose two of the 5 piles to remove, and place them at the bottom of the remaining deck of cards. Then randomly sort the 3 remaining piles into a row (ie 1, 2, 3). Flip the top cards of piles 1 and 3, and add their values to a value of 10–for example, a Q and a 5 would result in a cumulative value of 27.
Next, deal off a number of cards from the deck equal to the cumulative value of the previous step.

The number of cards remaining in the deck will be small. The value of the top card of pile 2 will be equal to the number of remaining cards.

3 Comments

2023/11/30

23:00 UTC

23:00 UTC

0

Im having a brain attack. Local artist posted their spotify stats, they had 46500 streams and 1800 hours listened. How long on average would someone have listened to their songs?

5 Comments

2023/11/30

21:20 UTC

21:20 UTC

0

1 Comment

2023/11/30

21:02 UTC

21:02 UTC

1

Request on-call at work

So we have an on call policy at work where we have 6 people in the rota. If I were to do the Christmas week on call this year, how many years would it be before I have to do it again? And what happens when they add a 7th and 8th person?

1 Comment

2023/11/30

21:02 UTC

21:02 UTC

1

Let's assume they are McDonald's-style fries (not wedges or crinkly fries).

4 Comments

2023/11/30

20:53 UTC

20:53 UTC

12

3 Comments

2023/11/30

20:48 UTC

20:48 UTC

26

5 Comments

2023/11/30

20:39 UTC

20:39 UTC

1

a fortnite impulse grendate btw

1 Comment

2023/11/30

20:27 UTC

20:27 UTC

14

8 Comments

2023/11/30

18:15 UTC

18:15 UTC

1

Let's say hypothetically there's a square mirror 10 metres across on the moon, how much energy would you need to put onto the laser for it to reflect off of it and come back to earth with enough energy to still be seen as a ray of light (and not just a dot on the ground) by an human eye distant 1m from the ray itself?

4 Comments

2023/11/30

17:18 UTC

17:18 UTC

2

5 Comments

2023/11/30

16:56 UTC

16:56 UTC

12

Assuming this person did not create a custom license plate. What is the probability?

9 Comments

2023/11/30

16:26 UTC

16:26 UTC

1

1 Comment

2023/11/30

15:09 UTC

15:09 UTC

6

5 Comments

2023/11/30

14:57 UTC

14:57 UTC

1

I tried searching, but did not find anything, I think because of too many big keywords for the internet.

Correct my logic please, but if the government pays an employee, and the employee pays federal taxes, the employee pays themselves some small percent?

I was considering the following:(employee gross yearly pay) / (government yearly revenue) = (fraction employee is paid from total revenue)

(fraction employee is paid from total revenue) * (federal taxes paid yearly) = (fraction of money employee paid themselves)

(fraction of money employee paid themselves) * (employee gross yearly pay) = (money employee paid themselves)

I assumed that if the government collects revenue, then divides that total to all destinations, the destination includes some small percent for a single employee.

I know this has some logical leaps and simplifications (and errors). I don't have the brain power to make better assumptions.

3 Comments

2023/11/30

14:38 UTC

14:38 UTC

1,018

I'm assuming it was some sort of factory error, but what IF it was legit?

80 Comments

2023/11/30

14:22 UTC

14:22 UTC

2

I thought of this question randomly. And it has been stumping me. It seems like there should be an elegant/obvious solution, but I have tried a lot of approaches and not really gotten anywhere.

2 Comments

2023/11/30

14:22 UTC

14:22 UTC

2,924

Inspired by this picture I saw on Nextdoor. I don’t know if 3 cubes are enough because we need to represent 7-9 twice (tens and one’s place). But we only need 1-3 in the hundred’s place so we have 3 extra spaces on that cube.

Follow up question: if 3 cubes aren’t enough, what about 2 cubes+ 1 7-sided dice? What’s the fewest number of faces required?

108 Comments

2023/11/30

13:45 UTC

13:45 UTC

0

The scale of 52! has always fascinated me. A small deck of cards procuring such infinite possibilities is quite the wonder. I've often heard it thrown around that if you shuffle a deck of cards properly there's almost a guarantee that the combination has never existed before in space and time. My question is how much can the length of a human life decrease the probability of getting a unique arrangement. Suppose a universe where the playing cards have just been created and a child was born with the soul purpose of shuffling the cards and creating new arrangements. Say he starts from the age of 5 and keeps at it till he's a 105 years of age. Let us also assume that his speed of shuffling is constant. I imagine the quickest way for new combinations would be to just keep displacing one card from the top to anywhere else (or maybe I'm completely off and it's some other algorithm). So in his 100 years of life how much of an impact would he be able to place on the probability of a unique arrangement?

9 Comments

2023/11/30

13:16 UTC

13:16 UTC

0

12 Comments

2023/11/30

12:15 UTC

12:15 UTC

706

35 Comments

2023/11/30

10:10 UTC

10:10 UTC

8

I took this picture from internet just wanted to know it's accuracy in representation

3 Comments

2023/11/30

09:30 UTC

09:30 UTC

0

We were traveling around on Madagaskar, on a small national flight from Nosy Be to Antananarivo, we met our neighbors! We from Belgium, so Madagaskar is pretty far away. My girlfriend yelled something along the translated lines of "omg, what are the odds?" We make one international holiday per year, and our neighbors do too. What are the odds we meet on Nosy Be?

How do we go about calculating this? If there are additional detail you need to improve the calculations, feel free to ask.

4 Comments

2023/11/30

08:00 UTC

08:00 UTC