Results 1 to 4 of 4

Math Help - Struggling with Rate of Change for Rational Functions

  1. #1
    Newbie
    Joined
    Mar 2010
    Posts
    6

    Struggling with Rate of Change for Rational Functions

    Hey guys, I've been googling for hours on how to solve this with no luck!

    I need to find the average and instantaneous rate of change of a rational function:

    As you get farther from Earth’s surface, gravity has less effect on you. For this reason, you actually weigh less at higher altitudes. A person who weighs 55kg can use the function:

    W(h) = 6400(55)/ (h + 64000)

    to find their weight, W in kgs, at a specific height, h in feet above sea level, above the Earth’s surface.

    Find the average rate of change from heights of 750 ft to 1200 ft above sea level, and find the instantaneous rate of change at 1200 ft above sea level.

    I know that average rate of change is [W(1200)-W(750)]/1200-750 right? But when I plug in values for h the answers aren't even close. I know I'm missing something but I just don't understand what!

    The answer posted is -0.0065 but I get like -0.00008
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,802
    Thanks
    691
    Hello, OmegaCenturion!

    I think you have a typo in the formula . . .


    I need to find the average and instantaneous rate of change of a rational function:

    As you get farther from Earth’s surface, gravity has less effect on you.
    For this reason, you actually weigh less at higher altitudes.

    A person who weighs 55 kg can use the function: . W(h) \:=\: 6400\,\frac{55}{h + {\color{red}6400}}

    to find their weight, W in kgs, at a specific height, h in feet above sea level, above the Earth’s surface.

    (a) Find the average rate of change from heights of 750 ft to 1200 ft above sea level.

    (b) Find the instantaneous rate of change at 1200 ft above sea level.

    Now try it . . .

    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2010
    Posts
    6
    Hi, I'm fairly positive I typed in the formula correctly, it was 64,000 not 6,400. Is it a matter of simply plugging in h values or is there some algebra involved? Perhaps I will post another question from the same worksheet as I'm unable to solve any of them

    it looks like this:

    6400(55)
    ________

    h + 64,000


    Airbags are a standard safety feature of most cars. Without airbags, a person or object would move forward at the velocity that the car is moving. A person inside a car traveling at 8m/s and weighing 8000kg would follow the function:

    v (m)= [8000(m -1)] / [8000(m+1)] x 5

    where m represents the mass of the person. Find the average rate of change as the mass of the person changes from 57 kg to 75 kg, and the
    instantaneous rate of change at 75 kg.

    How do you use that special notation? it would help a lot to know how to write like that
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Mar 2010
    Posts
    6
    Can anyone help?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: April 12th 2011, 09:51 AM
  2. Rational average rate of change problem
    Posted in the Algebra Forum
    Replies: 7
    Last Post: April 10th 2011, 03:00 PM
  3. average rate of change - evaluating functions
    Posted in the Calculus Forum
    Replies: 3
    Last Post: January 26th 2011, 02:50 PM
  4. Rate of change using trig functions.
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: March 14th 2010, 08:38 PM
  5. rate of change and functions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 31st 2010, 10:42 AM

Search Tags


/mathhelpforum @mathhelpforum