ANSWERS: 2

The 350 million is a red herring. The chances that 2 or more of 12 people will have the same birthday is 1(the chance that they all have different birthdays). Ignoring the 29th of February, the chance that they all have different birthdays is given by: (365/365)*(364/365)*(363/365)*...*(354/365) = 0.833 So the chance that two or more have the same birthday is 0.167 which is about one in six. (feb 29th makes a tiny difference to that)

again ignoring feb 29, it is actually 1/365 because you take the first person and the probability he has a birthday is 365/365. take that times the probability that someone has the exact same birthday (which is 1/365 because the date must be the same) so 1*(1/365)= 1/365
Copyright 2018, Wired Ivy, LLC