Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The birthday problem concept question

  1. Jun 5, 2014 #1
    Let A(i) be the event that the first ith person have different birthdays for i=1,2,3...,n.
    We note that A(i+1) is a subset of Ai such that Ai(A(i+1))= A(i+1)

    I wonder why A(i+1) is a subset of Ai. If the first 3 people have no birthdays in common, shouldn't that also mean the first 2 people doesn't either? By that logic, shouldnt Ai be the subset of A(i+1)?
    Last edited: Jun 5, 2014
  2. jcsd
  3. Jun 6, 2014 #2


    User Avatar
    Science Advisor

    Your reasoning is correct up to the conclusion. Ai includes i+1 people who have same birthday as one of the first i, as well as all of A(i+1), therefore Ai is the bigger set.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook