The birthday problem can be formulated as follows:

In a class there are n students. What is the probability that at least two students were born on the same day of the year?

For simplify the math, without changing the result significantly, let's assume that year is always 365 days long (no February 29 birthdays) and let's assume that a person has an equal chance of being born on any day of the year, although some birthday may be slightly more likely than others.

If the students are 366 the probability would be equal to 1. If there is just 1 student the probability would be equal to 0.

Which is the n of student needed for the probability to be 0.5?

Most people would answer 183 and explain their answer saying that with this number of student the probability must be 0.5 because of this proportion:

366 : 1 = x : 0.5

This is the correct answer to a very different question: "How many student do you need in a class so that there is a 0.5 probability that one of them will share YOUR birthday?" If instead there are no restrictions on which two students will share a birthday, it makes a very big difference. If we take a class of 23 students there are 253 different ways of pairing two people together, and that gives a lot of possibilities of finding a pair with the same birthday.

To solve the birthday problem we need to use one of the basic rules of probability: the sum of the probability that an event will happen and the probability that the event won't happen is always 1. (In other words, the chance that anything might or might not happen is always 100%). If we can work out the probability that no two people will have the same birthday, we can use this rule to find the probability that two people will share a birthday:

P(event happens) + P(event doesn't happen) = 1
P(two people share birthday) + P(no two people share birthday) = 1 P(two people share birthday) = 1 - P(no two people share...

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“A Very Happy Birthday”
A Critical Analysis of “Birthday Girl” by Haruki Murakami
Haruki Murakami’s “Birthday Girl” is a piece that can take the reader into the past and help us analyze if any of our wishes ever came true. Hopefully we all reach those birthday milestones and we get whatever it is we wished for. The main character in this story has reached an important milestone...

...Our topic of discussion is “BIRTHDAY CELEBRATION,”We have two opinion polls,
(A)Some of us think that there is no harm in celebration
(B)While others think we shouldn’t celebrate&I belongs to the this category.
& as I never celebrate birthday so I will talk about the disadvantages of Birthday celebration ,because I am against of birthday celebration..
First of all we should know the routes of the custom which we are...

...“Birthday Party” by Katherine Brush uses literary devices such as tone, point of view, diction, and sensory details to achieve her purpose.
The title of this short story is very deceiving the tone is different from the tone of the story. The tone changes from happy to sad as soon as the cake is brought out. The women tried to show affection and love towards her husband by the cake but it was basically turned down. The point of view is through a random person who doesn’t know...

...Analysis of “Let’s get the (Birthday) party
started”
A short story by Dave Barry
Childhood amnesia is a well known fact. Most adults are unable to remember
infancy or toddlerhood. Therefore, one wonders whether it is even worth to celebrate
a toddler’s birthday. Dave Berry’s short story “Let's get the (birthday) party started
right” is mostly a low level comedy text that uses caricatures, one liners and hyperboles
to communicate the idea that...

...LESSON PLAN
Subject : English 4
Theme : Birthday Party
Integrated skills : Reading
Functions : to enable the students to reordering jumbled sentences based on the pictures.
Vocabulary : preparing, making, remember, praying, present, ribbon, clown, birthday party, candle
Media : flashcards and pictures
No Teaching Phase Teacher’s Instruction Student Activities Teaching Aids
1 Pre-Teaching
Greet the students:
“Hello good...

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My Ultimate Birthday Surprise
I had gone to spend the week with my cousin, Brandon, and his wife, Jennie the summer of my sixteenth birthday. I had no idea that Brandon had the most thoughtful and extravagant birthday gift I could ever imagine. Brandon had, without his wife’s knowledge, set up an appointment for Jennie and me to go skydiving. I had always wondered if I would ever have the courage to jump out of an airplane at 13,000 feet in...

...fulfill your unique mission. So a birthday is a momentous occasion, to be commemorated just as a nation commemorates its birth or as an organization celebrates its founding. Still, it is much more than an occasion to receive gifts. It is a chance to remember the day that a major event occurred, to celebrate and give thanks and to reflect upon how well we are fulfilling our calling.
Because time itself is like a spiral, something special happens on your birthday...

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Drag’s Birthday Surprise:
A Tiberius Story
by Keith Harvey
Sometimes the postman came to Tiberius’ house, but not very often. Occasionally he had a letter from a friend who had moved away to another village and sometimes his aunt would send him a letter, or even a parcel!
Tiberius was halfway through his breakfast of cheeseflakes when he first heard the postman’s cheery whistle.
‘Great!’ thought Tiberius. ‘It sounds like a letter or, even better, a parcel is coming my...