Please help me if you can!
2007-09-16 04:32:50 · 8 answers · asked by A.M.P. 3 in Science & Mathematics ➔ Mathematics
Well, I think the question you are asking is, how many people are needed for the probability to be at least 50%. The answer to that is 23. Most folks are surprised it is that low. Google "Birthday paradox" if you want more information.
2007-09-16 04:43:43 · answer #1 · answered by Anonymous · 0⤊ 0⤋
I think you might mean 'What is the smallest number of peole in a room where the probability of two of them having the same birthday is 50%.
The answer is, surprisingly less than thirty. ((Answers above give the number as 23)
This seems strange at first, because 23 goes into 365 fifteen times, so why isn't the probability 1 in 15?
There IS a probability of 22 in 365 of one person having the same birthday as the FIRST person; but then a 21 in 364 chance of someone having the same birthday as the second person, and a 20 in 363 chance of someone having the same birthday as the third person, and so on. Add all the probabilities together, and you come up with a probability of about 1 in 2 for thirty people.
.
2007-09-16 11:52:08 · answer #2 · answered by AndrewG 7 · 0⤊ 0⤋
Answer: 23!!
I found the answer right off some kind of website. I forgot the site though lol... SORRY!
23 is still correct.
If you're wondering how to actually do it...
Instead of finding the probability on that two people will have the same birthday... Find the probability they are different.
1 - (365/365)(364/365)(363/365)... When the value of this difference is less than 50... Count the number of fractions you multiplied. That will be your answer.
Now that I think of it... it actually doesn't have enough information to be answered lol.
Well whatever the probability is, you keep multiplying and subtracting until you get a number right below 10(or on it). The number of fractions you multiplied is your answer.
2007-09-16 11:43:02 · answer #3 · answered by UnknownD 6 · 0⤊ 0⤋
7
2007-09-16 11:41:06 · answer #4 · answered by Kristen 2 · 0⤊ 0⤋
I dont think that is the full question or you have worded it wrong
less than 23 the probability is less than 50/50
23 it is 50/50
more than 23 the probability is more than 50/50
(i think)
EDIT - I just worked it out, yes it is 23
Infact if you get 50 people in a room, surprisingly to most, the probablility of them two of them having the same birthday is 97%!!!!
2007-09-16 11:43:14 · answer #5 · answered by Anonymous · 0⤊ 0⤋
If there are 365 people in a room, the chances that two people would have the same birthday would be 99.97758617% (the difference between that percentage and 100% would be if one of the persons was born on February 29th)!
2007-09-16 11:57:36 · answer #6 · answered by trebor namyl hcaeb 6 · 0⤊ 0⤋
I'd love to help, but you didn't finish the question.
"...where the probability of two of them having the same birthday..."
Is what?
50%?
10%?
Without knowing the information you are looking for, it's impossible to give you an answer.
I've a feeling that you left out a vital word or two.
2007-09-16 11:41:55 · answer #7 · answered by Anonymous · 0⤊ 0⤋
366?
2007-09-16 11:41:19 · answer #8 · answered by Anonymous · 0⤊ 1⤋