1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Probability Question - Need help !

  1. Jan 15, 2006 #1
    Probability Question - Need help plz!

    There are three boxes with 2 cupcakes in each one of them:

    First box: 2 chocolate cupcakes
    Second box: 1 chocolate, 1 vanilla
    Third box: 2 vanilla cupcakes

    A person randomly opens up a box and selects one cupcake. It is a chocolate cupcake. She then pulls out the remaining cupcake in the same box. What is the probability that it is a chocolate cupcake?

    Ok here is what I think...
    Since the question is only asking for the probability that the second cupcake in the box is chocolate, we don't have to worry about the first step of picking the right box. Therefore, the probability should be 1/2 because you can either pick a vanilla or a chocolate, but it doesn't really sound convincing....
     
    Last edited: Jan 15, 2006
  2. jcsd
  3. Jan 15, 2006 #2

    EnumaElish

    User Avatar
    Science Advisor
    Homework Helper

    It's a conditional prob. question, "what is the prob. of the box being the choc. box given a choc cake has been picked?"

    P(Choc box|a choc cake has been picked) = P(Choc box and a choc cake has been picked)/P(a choc cake has been picked) = P(Choc box)/(3/6) = (1/3) / (1/2) = 2/3.

    See this example.
     
    Last edited: Jan 16, 2006
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?