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

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