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Math function problem homwork

  1. Nov 17, 2008 #1
    1. The problem statement, all variables and given/known data

    A telephone company charges a fee of $29.99 per month for basic local service. A fee of $4.95 per month is added for customers wanting up to 500 minutes of long distance at $0.04 minute.

    a. Write a cost function to determine the amount a customer with the local and long distance plans would be charged that is based on the number of long distance minutes used each month.
    b. Use the function you’ve written to determine how much a customer making 345 minutes worth of long distance calls would be charged for the month.

    2. Relevant equations

    3. The attempt at a solution

    C= p+f+(.04x)
    C=29.99+ 4.95+ (.04x)
    C=29.99+ 4.95+ (.04x345)
    C= 29.99+ 4.95+ 13.80
    C= 48.74
    Not sure if there needed to be an x after the C or not.
  2. jcsd
  3. Nov 17, 2008 #2


    Staff: Mentor

    Re: functions

    This is the answer to part a, except that it doesn't take the limit of 500 minutes into account. For example, by your formula above, a customer who used 1000 minutes would have a bill of 29.99 + 4.95 + .04*1000 = 29.99 + 4.95 + 40 = $74.94.

    As I mentioned, this ignores the 500-minute limit. To take that into account, consider the domain for this function.
    You were asked to come up with a function, so for part a, I would write it like this:
    C(x) = 29.99 + 4.95 + .04x, <restrictions on x>
    For part b, you are supposed to evaluate your function for x = 345, so you want C(345).
    Be sure to include the appropriate units.

    BTW, this is not a calculus problem.
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