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Should add the probabilities or multiply them?

  1. Apr 18, 2009 #1
    Hello. I'm new to this forum and I need help on this question:

    Team A is playing a football match against Team B. if the probability that A will win is 4/11 and the probability that B will win is 2/11, find the probability that the match will be a draw.


    I'm not sure if I should add the probabilities or multiply them, and then subtract the result from 1.


    So it's either:

    A) P(match will be a draw)= 1-(4/11 +2/11)
    =5/11

    or:

    B) P(match will be a draw)= 1-(4/11)(2/11)
    =113/141

    Thanks a lot for any assistance provided!

    Ps: Is this considered as asking for answers directly?
     
    Last edited: Apr 18, 2009
  2. jcsd
  3. Apr 18, 2009 #2
    Re: Probability

    Here is a Hint:

    Let Pa be the probability that team A wins.
    Let Pb be the probability that team b wins.
    Let Pd be the probability of a draw.

    You sample space has only three events: { A wins, B wins, Draw}

    Exactly one of the three events will happen. In other words "A wins OR B wins OR Draw".

    So, what can you say about Pa + Pb + Pd ???
     
  4. Apr 18, 2009 #3
    Re: Probability

    Oh! So Pa + Pb + Pd = 1, therefore Pd= 1-(4/11 +2/11)
    =5/11
    Thank you very much!
     
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