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Easy Probability Question

  1. Apr 19, 2009 #1
    A set of 1000 cards, numbered 1 through 1000 are distributed among 1000 people. Compute the expected number of cards that are given to people whose age matches the number on the card.


    So the relevant formula is expected value, but its conditioned because of the ages. So I assumed that the age range was between 1-100.
    So n* P{card reads age | age <= 100)

    Is this the correct assumption?

    So would the probability be 1/1000 / 100/1000 = .01
     
  2. jcsd
  3. Apr 20, 2009 #2
    The answer is 1.

    Hints:

    Consider the random variable N_i = number of people age i who get a card with their age.

    We want E(N_1 + N_2 + ... + N_1000).
     
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