IJPAM: Volume 81, No. 6 (2012)
Department of Business Information
Faculty of Information Management
Osaka University of Economics
2, Osumi Higashiyodogawa Osaka, 533-8533, JAPAN
Abstract. This article presents 2 unexpected probabilities. If there are at least 23 people in a class, then the probability that there is a shared birthday exceeds one half. This is explained by the idea of complementary events. What are the chances of there being a student who ends up in the same seat when everyone in the class is reseated? This probability is around irrespective of the number of students, and was solved by Montmort (1708).
Received: August 18, 2012
AMS Subject Classification: 60A02, 00A09, 97A20
Key Words and Phrases: likelihood of shared birthdays, complementary events, probability of ending up in the same seat, Montmort's theory, Venn diagram
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Source: International Journal of Pure and Applied Mathematics
ISSN printed version: 1311-8080
ISSN on-line version: 1314-3395