Results 1 to 3 of 3

Math Help - Statistics & probabolity problems, please help

  1. #1
    Newbie
    Joined
    Sep 2009
    Posts
    4

    Statistics & probabolity problems, please help

    I have these problems to turn in for tomorrow. I don't know the best way to solve them.
    Please see if you can solve them and post your results along with calculations.

    Problem 1:

    In bowl A there are 4 red balls, 3 blue balls and 2 green balls.
    In bowl B there are 2 red, 3, blue and 4 green.
    One ball is taken from bowl A and put into bowl B.
    After this is done one ball is taken from bowl B.
    What are the odds that the ball, taken from bowl B, is red?


    Problem 2:

    Given are:

    S1 = {1,2,3,4}
    S2 = {1,2,3,4,5,6}
    S3 = {1,2,3,4,5,6,7,8}

    We pick one number randomly from S1, where there is an equal chance of picking any one number. We do the same with S2 and S3.
    What are the odds that the sum of the numbers we picked are equal to 5?


    Thanks in advance for all your help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Grandad's Avatar
    Joined
    Dec 2008
    From
    South Coast of England
    Posts
    2,570
    Thanks
    1
    Hello Lesarinn

    Welcome to Math Help Forum!
    Quote Originally Posted by Lesarinn View Post
    I have these problems to turn in for tomorrow. I don't know the best way to solve them.
    Please see if you can solve them and post your results along with calculations.

    Problem 1:

    In bowl A there are 4 red balls, 3 blue balls and 2 green balls.
    In bowl B there are 2 red, 3, blue and 4 green.
    One ball is taken from bowl A and put into bowl B.
    After this is done one ball is taken from bowl B.
    What are the odds that the ball, taken from bowl B, is red?
    There are two different cases to consider:

    • (i) The ball taken from bowl A is red; and then the ball taken from bowl B is red.


    • (ii) The ball taken from bowl A is not red; and then the ball taken from bowl B is red.

    Work out the probabilities p_1 and p_2 that the ball taken from A is (i) red, and (ii) not red. Then, by considering the number of red balls in bowl B in each case (i) and (ii), work out the probabilities q_1 and q_2 that the second ball is red.

    Finally, multiply p_1 by q_1; multiply p_2 by q_2; then add your answers to get the final answer. I reckon this comes out as \frac{11}{45}.


    Problem 2:

    Given are:

    S1 = {1,2,3,4}
    S2 = {1,2,3,4,5,6}
    S3 = {1,2,3,4,5,6,7,8}

    We pick one number randomly from S1, where there is an equal chance of picking any one number. We do the same with S2 and S3.
    What are the odds that the sum of the numbers we picked are equal to 5?


    Thanks in advance for all your help.
    Work out all the ways in which the total could be 5; then work out the probability that each of these sequences of numbers occurs. Finally add all your answers together to get the overall probability.

    I'll start you off. We could have:

    • 1,1,3. The probability of this is \tfrac14\times\tfrac16\times\tfrac18 = \tfrac{1}{192}.


    • 1,2,2. The probability of this is exactly the same: \tfrac14\times\tfrac16\times\tfrac18 = \tfrac{1}{192}


    • ... and so on.

    I reckon that the answer is \tfrac{5}{192}.

    Can you complete these now?

    Grandad
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2009
    Posts
    4
    This is exactly what I managed to come up with myself after I posted this thread.

    I am pretty sure that this is the right way to solve Problem 1.

    In Problem 2: Yeah I guess using the same method does seem to work.

    Thank you Grandad

    Problems are solved.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Help - Problems in Statistics
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: August 9th 2009, 03:42 AM
  2. Statistics Probabilities Problems
    Posted in the Statistics Forum
    Replies: 1
    Last Post: March 29th 2009, 01:02 PM
  3. 2 statistics problems I need help with
    Posted in the Statistics Forum
    Replies: 1
    Last Post: February 23rd 2009, 08:24 PM
  4. Statistics Problems
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 12th 2008, 08:29 AM
  5. more statistics problems
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: June 9th 2008, 06:25 PM

Search Tags


/mathhelpforum @mathhelpforum