1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Probability Problems

  1. May 2, 2005 #1
    A viewer preference survey conducted by a cable-television network revealed that 46% of viewers watch sports, 31% watch comedy, and 33% watch drama. Of these viewers, 13% watch sports and comedy, 9% watch comedy and drama, and 11% watch sports and drama. Suppose 20% of viewers watch none of these 3 types of shows. What is the probability that a randomly selected person watches all three?

    I have no idea how to do this problem. I tried using a venn diagram, but that didn't seem to work..

    And for this problem:
    In a card game, a hand of 5 cards contains at least 2 spades. What is the probability that there are exactly 4 spades in that hand?

    I tried doing 5C4(13/52)^4(39/52), but it wasn't correct..
  2. jcsd
  3. May 2, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    I think you can do the first one with a Venn diagram approach. Draw three circles with mutual overlap and label the 7 separate regions as A,B,C,D,E,F, and G, with G in the middle (see diagram). You are told that the total region is .80, and you are told the area of each circle. The way I drew mine these are

    A + D + E + G = .41
    B + F + E + G = .31
    C + D + F + G = .33

    Add these three

    A + B + C + 2D + 2E + 2F + 3G = .105


    A + B + C + D + E + F + G = .80

    Take the difference.

    D + E + F + 2G = .25

    The rest of the problem involves finding D + G, E + G, and F + G from the information given, and solving for G

    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook