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Homework Help: Describing derivatives in practical terms

  1. Oct 5, 2008 #1
    1. The problem statement, all variables and given/known data

    Suppose C(r) is the total cost of paying off a car loan borrowed at an annual interest rate of r%. What are the units of C '(r)? What are the units of C'(r)? What is its sign?

    2. Relevant equations
    C'(r)=dC/dr


    3. The attempt at a solution

    So, I figured:

    C'(r) = dC/dr
    Which is dollars over interest rate(?)...which seems kinda awkward to me. I'm wondering if theres a better solution for what the units of C'(r) would be. (dollars per percent interest?)

    And I'm not sure what is meant by "What is it's sign"?
     
  2. jcsd
  3. Oct 5, 2008 #2

    Redbelly98

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    What are the units of r?

    "What is it's sign" means is it positive or negative ... or zero.
     
  4. Oct 5, 2008 #3
    r is a %
     
  5. Oct 5, 2008 #4

    Redbelly98

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    Okay. So the units of C/r would be ... ?
     
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