how many people in a room does it take for there to be a 50/50 chance of 2 people sharing a birthday? show and explane work

yixz33
Jun 2, 2014

#9**+5 **

How rude, how rude!

Still, 2 can play at thine game.

Check the points again dear Sir.

And the Lady still hath her head!

Have thou found the Roman zero amounst Zeus's offerings yet?

Thou waste time here annoying the Queen when thou should be attending thine own most urgent tasks.

Be off with you Sir Headless CPhill!

You are but a knat upon Her Royal steed!!

Melody
Jun 2, 2014

#1**+5 **

23 people and the reasoning (ignoging leap years) goes :- Start with one person in a room. Add a second person and the probability that he has a different birthday is 364/365. Add a third and the probability that he has a different birthday to the first two is 363/365. The probability that there are now no duplicate birthdays is (364/365)*(363/365). Add a fourth and the probability that he has a different birthday to the first three is 362/365. The probability that there are now no duplicate birthdays is (364/365)*(363/365)*(362/365). etc. The probability that there are no duplicate birthdays falls below 50% when the 23rd person arrives.

Melody
Jun 2, 2014

#2**+5 **## Look what Sir CPhill just sent me!

## How dare he talk to the Lady of the Land like that!

## Guards! Guards!

## Off with his head!

*Queen Guinevere.*

"CHEAT!!!

CHEAT!!!

CHEAT!!!!

.....This "procedure" violates "forum protocol"......

I'll "out" you on the forum, if you're not careful!!

At least give me some credit for remembering that it WAS 23 !!!"

Melody
Jun 2, 2014

#3**+5 **

....And the probability that Melody got this answer off the internet =

[(10000)^{(1/2)}] %

CPhill
Jun 2, 2014

#5**+5 **

Let us calculate another "probability"........

Question: What is the probability that, of N forum members, one steals another's idea and makes it his/her own ???

P.S. ......it's more than 50%....and we don't even need 23 people, either ......!!!

CPhill
Jun 2, 2014

#7**+5 **

This cheeky anonymous person who gave themselves 5 points just for asking a question.

Should shower us both in points for out supreme efforts here!

You can have yours posthumously!

Melody
Jun 2, 2014

#8**+5 **

Checketh thou point totals on the question under scrutiny, again, Fair Lady !!!

It appearest that MINE hath increased without bound.........while THINE have suffered a most frightful decline....

CPhill
Jun 2, 2014

#9**+5 **

Best Answer

How rude, how rude!

Still, 2 can play at thine game.

Check the points again dear Sir.

And the Lady still hath her head!

Have thou found the Roman zero amounst Zeus's offerings yet?

Thou waste time here annoying the Queen when thou should be attending thine own most urgent tasks.

Be off with you Sir Headless CPhill!

You are but a knat upon Her Royal steed!!

Melody
Jun 2, 2014