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Don't understand

  1. Oct 27, 2007 #1
    dont understand

    For the following function, C computes the cost in millions of dollars of implementing a city recycling project when x percent of the citizens participate.
    Using this model, approximately what is the cost if 60% of the citizens participate?
    Using this model, estimate the percentage of participation that can be excepted if $5 million is spent on this recycling project? Set up an equation and solve algebraically. Round to the nearest whole percent
     
    Last edited: Oct 27, 2007
  2. jcsd
  3. Oct 27, 2007 #2

    symbolipoint

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    Do you have a function definition for C? Do you have sufficient information to find the function C?

    Your information seems to become:
    C=f(x); what is f(0.60)? what is x when 5=f(x)?... in other words, if C=5, what is f(x)?

    More information is needed.
     
  4. Oct 29, 2007 #3
    C(x)=1.5x/100-x

    his is the formula the book gives me
     
  5. Oct 29, 2007 #4

    Zurtex

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    So x is the percentage and C is the total cost.

    Replace x with 60 in the formula and see what C is.
     
  6. Oct 29, 2007 #5
    i did that a got like .04 but to me that doesn't seem right
     
  7. Oct 29, 2007 #6

    Zurtex

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    I assume the formular to mean this:

    C(x)=(1.5x)/(100-x)

    Right? In which case put 60 in and work out again.
     
  8. Oct 29, 2007 #7
    this is what i did
    C(X)=1.5X/100-X
    C(60)=1.5*60/100-60
    C(60)=90/40
    C(60)=2.25
    C(60/60)=2.25/60
    C=.0375 OR .04
    so i'm suppose to put this in millions if i move the decimal point over six spaces then i get37,500 or 40,000
     
  9. Oct 29, 2007 #8

    Zurtex

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    I don't understand why you suddenly decided to divide it by 60 here, I also don't understand why you think: C(x/60) = C(x)/60
     
  10. Oct 29, 2007 #9
    isnt the x in front of the C a 60 so to get C by itself you divide
     
  11. Oct 29, 2007 #10
    No it isn't. The notation C(x) means that C is a function of x, it is not multiplication of C by x. Often in math we use a shorthand and refer to a function f(x) by merely f, that is what is happening when they ask you for the value of C whe x=60, or C(60), that is the function C(x) evaluated at the number 60, not C "times" 60.
     
  12. Oct 29, 2007 #11
    ok i think i get it now, so my answer would be 2.25, put that into millions and i get 2,250,000
     
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