#math trivia: The 20-student class gets the flu. Every day a different prime number of students is out sick. For how long can this go on? — Burt Kaliski Jr. (@modulomathy) September 10, 2012 There are eight different prime numbers less than or equal to 20 (2, 3, 5, 7, 11, 13, 17 and 19), … Continue reading →