Results 1 to 4 of 4

Math Help - elevator weight question! urgent help !

  1. #1
    Newbie
    Joined
    May 2008
    Posts
    2

    elevator weight question! urgent help !

    normal distribution... the max elevator weight cannot be greater than 1120kg or 16 people. suppose that the weights of lift users are normally distributed with a mean of 68kg and a standard deviation with 8kg.

    what is the probability that 16 people will exceed the weight limit of 1120kg?

    and also what is the probability that 18 people will not exceed the weight limit?


    p.s thank you for your help
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by tofustar View Post
    normal distribution... the max elevator weight cannot be greater than 1120kg or 16 people. suppose that the weights of lift users are normally distributed with a mean of 68kg and a standard deviation with 8kg.

    what is the probability that 16 people will exceed the weight limit of 1120kg?

    and also what is the probability that 18 people will not exceed the weight limit?


    p.s thank you for your help
    Weight of 16 people: X ~ Normal \left( \mu = 16 \times 68 = ...., \sigma = 16 \times 8 = ....\right).

    Calculate \Pr( X > 1120).


    Weight of 18 people: Y ~ Normal \left( \mu = 18 \times 68 = ...., \sigma = 18 \times 8 = .... \right).

    Calculate \Pr( Y < 1120).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by mr fantastic View Post
    Weight of 16 people: X ~ Normal \left( \mu = 16 \times 68 = ...., \sigma = 16 \times 8 = ....\right).

    Calculate \Pr( X > 1120).
    \sigma=8 \sqrt{16}

    or \sigma^2= 8^2 \times 16


    Weight of 18 people: Y ~ Normal \left( \mu = 18 \times 68 = ...., \sigma = 18 \times 8 = .... \right).

    Calculate \Pr( Y < 1120).
    same again but with 18 in place of 16.

    CB
    Last edited by CaptainBlack; September 18th 2009 at 09:50 AM.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by CaptainBlack View Post
    \sigma=8 \sqrt{16}

    or \sigma^2= 8^2 \times 16




    same again but with 18 in place of 16.

    CB
    Thanks for that catch. Careless of me. (Perhaps my evil nature asserting itself).

    @OP: X = W_1 + W_2 + .... + W_n \Rightarrow Var (X) = n Var (W) \Rightarrow sd (X) = \sqrt{n} sd (W)
    Last edited by mr fantastic; September 18th 2009 at 10:39 AM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Question about forumula for weight loss
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: December 22nd 2011, 09:05 PM
  2. The weight of H(X) does not exceed the weight of X?
    Posted in the Differential Geometry Forum
    Replies: 0
    Last Post: October 13th 2011, 10:59 AM
  3. Question on weight of coins
    Posted in the Algebra Forum
    Replies: 8
    Last Post: September 13th 2011, 06:36 PM
  4. [Solved]Simple Elevator Question
    Posted in the Statistics Forum
    Replies: 0
    Last Post: October 13th 2009, 04:27 PM
  5. Weight question(interesting)
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: April 7th 2008, 05:40 PM

Search Tags


/mathhelpforum @mathhelpforum