注目の話題: どうしても結婚したいです。; ホームランボールは小さな子供に譲るべきなの？？; わたしが悪いですか？

Science,English,and math Ⅱ

No.144　18/02/12 11:16
燻し銀三 ( 50代 ♂ Oe38xe ) あ+あ-

【Untrustworthy intuition.】

《There is a class composed of 40 students. The probability that a student’s birthday is same with other one is no less than 89%.》

Each day when the three students were born are irrelevant each other,so the probability that the birthday of the three students are different is 364-365ths×363-365ths.

Even if the number of the students increases by 40,we can calculate its probability. At least the two students’ birthday is the same is complementary event,if deducting its probability from 1,we can find the value we want.

If calculating the probability actually,the probability that the students who have the same birthday is no less than 89%.

By the way,my intuition prevents me from thinking it over mathematically, it can't be! To my sorrow,I can't express it theoretically. The ones who have the wrong impression like me may have prevented the society from developing. Some of them may have insisted on the Ptolemaic theory 天動説 even after the Copernican theory.