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Thread: Solving linear equation help! Dont know how to start problem

  1. #1

    Solving linear equation help! Dont know how to start problem

    Can anyone help me with this problem?

    Given:


    A person cuts a rope into two pieces that are equal in length. The first piece is 4 times the length of the personís forearm minus 1 inch. The second piece is 3 times the length of the personís forearm plus 15 inches.


    Task:


    1. Construct the linear equation that represents the situation in the given using x as the variable for the personís forearm.


    2. Solve the linear equation you constructed both algebraically and graphically to find the length of the personís forearm. Show your work.


    3. Briefly discuss whether or not your answer is reasonable.

  2. #2
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    Assume the ropes are cut into lengths "L" inch

    Assume the length of the persons forarm = x inch

    Then

    The first condition

    The first piece is 4 times the length of the personís forearm minus 1 inch

    gives you

    L = 4*x - 1................................................. (1)

    This is your first equation,

    Similarly, write the next equation - using the second condition.

    Then solve for 'A'.

    If you are still stuck, write back showing your work.
    ď... mathematics is only the art of saying the same thing in different wordsĒ - B. Russell

  3. #3
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    Subby means: then solve for "x"
    I'm just an imagination of your figment !

  4. #4
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    Re: Solving linear equation help! Dont know how to start pro

    Quote Originally Posted by agcustoms
    Can anyone help me with this problem?

    Given:


    A person cuts a rope into two pieces that are equal in length. The first piece is 4 times the length of the personís forearm minus 1 inch. The second piece is 3 times the length of the personís forearm plus 15 inches.


    Task:


    1. Construct the linear equation that represents the situation in the given using x as the variable for the personís forearm.


    2. Solve the linear equation you constructed both algebraically and graphically to find the length of the personís forearm. Show your work.


    3. Briefly discuss whether or not your answer is reasonable.
    Let x = length of the forearm in inches

    One piece of the rope is equal to 4 times the forearm length, minus one inch. So that piece has a length of 4x - 1

    The other piece is 3 times the forearm length, plus 15 inches. So that piece has a length of 3x + 15

    You're told that the two pieces are equal.

    So.....

    4x - 1 = 3x + 15

    Solve that for x.

  5. #5
    So I am lost, all I need to do is solve for x? That seems to simple! i'm lost.

  6. #6
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    I'll show you another problem

    solve for 'x' when

    3x + 3 = x + 5

    Isolate variables

    3x + 3 - x = x + 5 - x

    2x + 3 = 5

    Isolate numbers

    2x + 3 - 3 = 5 - 3

    2x = 2

    Isolate numbers again

    2x/2 = 2/2

    x = 1

    check

    3x + 3 = x + 5

    3*1 + 3 = 1 + 5

    6 = 6 .............checks
    ď... mathematics is only the art of saying the same thing in different wordsĒ - B. Russell

  7. #7
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    Quote Originally Posted by agcustoms
    So I am lost, all I need to do is solve for x? That seems to simple! i'm lost.
    I'm sorry....if you are "lost" trying to solve an equation like

    4x - 1 = 3x + 15

    then you probably need to ask your teacher for some extra help.

  8. #8
    Ok. I got this. Is this right? Can anyone I point me in the right path to answer C?

    A. Construct the linear equation that represents the situation in the given using x as the variable for the personís forearm.
    Let x = length of the forearm in inches

    One piece of the rope is equal to 4 times the forearm length, minus one inch. So that piece has a length of 4x - 1

    The other piece is 3 times the forearm length, plus 15 inches. So that piece has a length of 3x + 15

    You're told that the two pieces are equal.

    So.....

    4x - 1 = 3x + 15


    B. Solve the linear equation you constructed both algebraically and graphically to find the length of the personís forearm. Show your work.


    4x-1=3x+15 original equation

    4x-1-3x=15 subtract 3x from both sides

    4x-3x=16 add 1 to each side and subtract 3 from 4

    x=16


    C. Briefly discuss whether or not your answer is reasonable.

    Need help on this one

  9. #9
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    Quote Originally Posted by agcustoms
    C. Briefly discuss whether or not your answer is reasonable.
    Need help on this one
    Forearm = distance between elbow and wrist; mine's about 11 inches;
    so 16 inches must be for 7 feet plus basketball players!

    "One piece of the rope is equal to 4 times the forearm length, minus one inch. So that piece has a length of 4x - 1"

    4(16) - 1 = 63

    "The other piece is 3 times the forearm length, plus 15 inches. So that piece has a length of 3x + 15"

    3(16) + 15 = 63

    So not only is it reasonable, it is guaranteed correct
    I'm just an imagination of your figment !

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