Results 1 to 5 of 5

Math Help - Singapore Math models

  1. #1
    Newbie
    Joined
    Feb 2008
    Posts
    2

    Singapore Math models

    I am a parent of a 5th grade child in NC. She is in the Advanced math class. They are using singapore math model approch to word problems and I need help understanding the system.

    Here is her word problem for tonight:

    The cost of four watched and three chains is $510. The cost of three watches and four chains is $505. What is the cost of 1 chain?


    Please help me!!!!!

    Gary
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Eater of Worlds
    galactus's Avatar
    Joined
    Jul 2006
    From
    Chaneysville, PA
    Posts
    3,001
    Thanks
    1
    Set up a small system of equations letting w = watch and c = chain.

    Then you have:

    4w+3c=510

    3w+4c=505

    Now you have a small system of linear equations in two variables to solve.

    Do you or your daughter know how to solve this by elimination or substitution?.

    Wow, this is impressive for a 5th grader. You must be proud of her.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,911
    Thanks
    773
    Hello, Gary!

    I'm not familiar with the Singapore Math Model approach.
    I'll give you a standard one . . .


    The cost of four watches and three chains is $510.
    The cost of three watches and four chains is $505.
    What is the cost of one chain?

    Let W = cost of a watch.
    Let C = cost of a chain.

    The cost of four watches and three chains is $510.
    . . This is written: . 4W + 3C \:=\:510 .[1]

    The cost of three watches and four chains is $505.
    . . This is written: . 3W + 4C \:=\:505 .[2]

    We have a system of equations . . .

    \begin{array}{cccc}\text{Multiply [1] by -3:} & \text{-}12W - 9C & = & \text{-}1530 \\ \text{Multiply [2] by 4:} & 12W + 16C & = & 2020 \end{array}

    Add the equations: . 7C \:=\:490\quad\Rightarrow\quad C \:=\:70


    Therefore, the cost of one chain is $70.

    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Feb 2008
    Posts
    2
    I can handle those. Algebra is what I am used to. I am just lost with the model approach.

    Quote Originally Posted by galactus View Post
    Set up a small system of equations letting w = watch and c = chain.

    Then you have:

    4w+3c=510

    3w+4c=505

    Now you have a small system of linear equations in two variables to solve.

    Do you or your daughter know how to solve this by elimination or substitution?.

    Wow, this is impressive for a 5th grader. You must be proud of her.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Feb 2007
    Posts
    2
    One possible method

    watches |-------|
    chains |----|

    |-------|-------|-------|-------|----|----|----| $510
    |-------|-------|-------|----|----|----|----| $505

    Rearrange

    |-------|-------|-------|----|----|----|-------| $510
    |-------|-------|-------|----|----|----|----| $505

    Difference between the two bars is difference between one watch and one chain.

    510 - 505 = 5

    A watch is $5 more than a chain.

    4 watches, then, would be the same as 4 chains + 4 x $5, or 4 chains + $20

    |----| 5 |----| 5 |----| 5|----| 5|----|----|----| $510

    7 chains = $510 - $20 = $490
    1 chain = $490/7 = $70
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. I need help with function models
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 24th 2010, 07:33 PM
  2. Math models and equations
    Posted in the Algebra Forum
    Replies: 3
    Last Post: January 14th 2009, 06:48 PM
  3. models
    Posted in the Differential Geometry Forum
    Replies: 0
    Last Post: February 17th 2008, 05:19 PM
  4. Replies: 2
    Last Post: July 17th 2007, 06:11 AM
  5. Need help Mathematical Models!
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: November 27th 2006, 04:50 AM

Search Tags


/mathhelpforum @mathhelpforum