Results 1 to 3 of 3

Math Help - weighing?

  1. #1
    Junior Member
    Joined
    Oct 2008
    Posts
    38
    Awards
    1

    Unhappy weighing?

    A jar filled with water weighs 10 pounds. When one-half of the water is poured out, the jar and remaining water weigh 5 3/4 pounds. How much does the jar weigh?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,835
    Thanks
    1604
    Quote Originally Posted by fecoupefe View Post
    A jar filled with water weighs 10 pounds. When one-half of the water is poured out, the jar and remaining water weigh 5 3/4 pounds. How much does the jar weigh?
    Let j = weight of jar
    Let w = weight of water when jar is full

    So we get the following system of equations

    j + w = 10
    j + \frac{1}{2}w = 5.75.

    Multiply the second equation by 2, and the system of equations becomes

    j + w = 10
    2j + w = 11.5

    Subtract the first equation from the second, you get

    2j + w - (j + w) = 11.5 - 10

    j = 1.5.


    So the weight of the jar is 1.5 pounds.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,915
    Thanks
    779
    Hello, fecoupefe!

    A jar filled with water weighs 10 pounds.
    When one-half of the water is poured out, the jar and remaining water weigh 5 pounds.
    How much does the jar weigh?

    Let J = weight of the jar.
    Let W = weight of the water.


    We have: . \begin{array}{cccc}J + W &=& 10 & {\color{blue}[1]} \\ J + \frac{1}{2}W &=& 5\frac{3}{4} & {\color{blue}[2]} \end{array}


    Subtract {\color{blue}[1] - [2]}: . \tfrac{1}{2}W \:=\:4\tfrac{1}{4} \quad\Rightarrow\quad W \:=\:8\tfrac{1}{2}


    Substitute into [1]: . J + 8\tfrac{1}{2} \:=\:10 \quad\Rightarrow\quad\boxed{ J \:=\:1\tfrac{1}{2}\text{ pounds}}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: December 28th 2011, 12:47 PM
  2. Weighing scores based on participation
    Posted in the Statistics Forum
    Replies: 3
    Last Post: July 1st 2011, 09:16 PM
  3. Weighing in....
    Posted in the Math Puzzles Forum
    Replies: 7
    Last Post: September 13th 2010, 07:02 PM
  4. Weighing in...
    Posted in the Math Puzzles Forum
    Replies: 2
    Last Post: August 10th 2010, 01:58 PM
  5. Percentage Growth / Weighing Function
    Posted in the Business Math Forum
    Replies: 8
    Last Post: April 14th 2005, 08:01 PM

Search Tags


/mathhelpforum @mathhelpforum