For the chance to be at least 50% that two people share the same birthday, there needs to be 22 people. For the chance to be exactly 100% that two people share the same birthday, there needs to be 366 people. If there was 365 people, there would be a very small chance that each person in the room would have different birthdays. With 366 people, there are not enough individual days for every person to have a different birthday, so there has to be at least one pair.
If there are 300,000,000 people in the US, then on average you share your birthday with over 82,000 people. Of course, if your birthday is 2/29, you would share it with about 1/4th of that number.
no
Everyone shares their birthday with someone or another.
justin
If they are related then they are twins?
If there are 300,000,000 people in the US, then on average you share your birthday with over 82,000 people. Of course, if your birthday is 2/29, you would share it with about 1/4th of that number.
no
Approxiamately six million people are born share a birthday so if you were born on that day you share your birthday with about six million people.
twins
Everyone shares their birthday with someone or another.
justin
If they are related then they are twins?
There cannot be a definite answer. There can only be a probabilistic answer of the number of people who might be expected to share a birthday. However, in order to do that it is necessary to know how many people there are in the school. And since you have not bothered to share that crucial bit of information, I cannot provide a more useful answer.
The probability that 25 random people don't ALL share the same birthday is: 1 - (1/365)**24, or about 0.999999999999999999999999999999999999999999999999999999999999968 However, I suspect you meant to ask "What is the probability that 25 random people all have different birthdays?" That is: 1 * (364/365) * (363/365) * (362/365) * ... * (342/365) * (341/365) = 0.4313 So about 43% of the time nobody will share a birthday, and 57% of the time, two or more people will share a birthday.
At least 100 all over the world.
estimating about 5000
A person shares their birthday with at least nine million different people around the world.