Help solving a word problem

I

isabelle2hot

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Nov 21, 2005
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Murrel's formula for calculating the total amount of rest, in minutes, required after performing a particular type of work activity for 30 minutes is given by the formula R(w) = , where w is the work expended in kilocalories per min. A bicyclist expends 8 kcal/min as she cycles home from work. Find R'(w) for the cyclist; that is, find R'(8).

a. 1.42 min2/kcal
b. 18.46 min2/kcal
c. 2.13 min2/kcal
d. 1.78 min2/kcal


When I did this problem I got B. I am not sure if this is right, can someone check my answer?

Isa :)
 
Perhaps you could suggest how you arrived at that possible response?
 
What did you get for the first derivative, R'(w)? You must be able to do that. There is a quotient rule just waiting to help you.
 
isabelle2hot said:
I am still totally confused, can someone help?
Click to expand...
If you are "totally confused", then how did you arrive at an answer? Since you arrived at an answer, you must have done... something....

Or were you just guessing, and are now hoping that a tutor will tell you which letter to circle...?

In hopes that the latter is not the case, I would ask that you kindly please reply showing the steps that you did. Thank you.

Eliz.
 
tkhunny said:
There is a quotient rule just waiting to help you.
Click to expand...
isabelle2hot said:
I can't get the first derivative.
Click to expand...

Try applying the Quotient Rule:

. . . . .For h(x) = f(x)/g(x), we have:


. . . . .\(\displaystyle \large{h'(x)\,=\,\frac{f'(x)g(x)\,-\,f(x)g'(x)}{[g(x)]^2}}\)


In your case, the variable is "w" instead of "x", and f(w) = 30(x - 4) and g(w) = w - 1.5.

Find their derivatives, and plug into the Rule.

Eliz.
 
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