How many people do I have to know if i wanted to be able to congratulate everyday (365 days) someone's birthday? I know the answer is probable by making a mathematical equation
eg) May 1st John's BDay,May 2nd Jessica's,May 3rd Tina's,May 4th Ray's etc
by 
josephlee1987
ANSWERS: 5
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If you pick and choose carefully the minimum number of people you will need to know is 365. Most likely 366, since there is that leap year day every 4 years.
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366 if you wish to cover leap year.
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I do not believe anyone is so stupid to need to ask this question! 365 days a year, one birthday per day, therefore the answer is blatantly obvious! -5 and pity I can not take more!
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The minimum is 365, obviously. But consider the probabilities... Say you find 364 friends each with a different birthday the chances of your next friend having a birthday on the missing day is only 1 in 365, so you need to make a lot of friends to stand a reasonable chance of filling that last day! Then consider 363 friends, only 1 in 181 chance of a new friend covering one of the two remaining days... and so on. So as you can see the answer will be a very large number. In fact I think to stand a 50% chance of having a birthday on each day of the year you need about 2300 friends! Consider it the other way around, if you have just 23 friends there is around a 50% chance that two will share a birthday, at 57 friends it is more than 99%, so you have a lot of 'wasted friends' building up along the way.
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ofcourse, everybody knows the minimum. my point of asking the question was not to find out the minimum but the maximum...or the most probable reliable number. "Godfather PartII" gave a good start, and i was looking for the number, with the equations. so help me out~ ^^
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