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Math Help - Function Problem! College Algebra.

  1. #1
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    Function Problem! College Algebra. SOLVED.

    I worked out the rest of the questions, but I am stuck on what to do at the end.

    The problem reads:

    Julie needs to hire a plumber. She is told that the cost of hiring the plumber, C , is a function of time spent on the job, t , in hours. The plumber charges a one time fee of $60 and an hourly rate of $50.

    The first question said "Determine a function which describes the total cost of hiring the plumber as a function of time"
    and I put "C=60 + 50X"

    So, the question that I am stuck on says

    Find the Value for C(0).

    ...I did this

    C(0) = 60 + 50x

    0 = 60 + 50x

    -60 = 50x

    -6/5 = X

    ...Is this right? I ... have no idea what I am s'posed to plug 0 into.
    I also tried

    C(0) = 60 + 50(0)

    C=60.

    ...The other questions are like

    question2) If plumber took 2 hours, how much did he make?
    c=60+50(2)
    c=160$

    question3)5 hours?
    c=60+50(5)
    c=310$

    question4)
    What if Julie paid him 210$?
    210=60+50x
    x=3 hrs.
    Last edited by Skyshadows; November 5th 2012 at 05:04 AM.
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  2. #2
    fkf
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    Re: Function Problem! College Algebra.

    We call C a function of time t hence we have
    C(t) = 60+50t

    You want to find C(0), so you put 0 instead of t into the function and get
    C(t) = 60+50t => C(0) = 60+50*(0) = 60$

    What you've done is calculating for which value of t in the function C(t) that gives us the value 0, or in mathematics C(t) = 0.

    On the other questions for example, if the plumper took 2 hours, we have C(2)
    C(t) = 60+50t => C(2) = 60+50*2 = 160$

    And on Q4 we want to solve C(t) = 210
    C(t) = 210 <=> 60+50t = 210 <=> t = 3 hours
    Last edited by fkf; November 5th 2012 at 04:41 AM. Reason: Spelling
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  3. #3
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    Re: Function Problem! College Algebra.

    Thank you!
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