Let's denote the diameter by D. Then (d-d-d-t ). You know and , so you can find .
Volume of a sphere:A snowball melts in volume @ 1 cm³/min. At what rate is the diameter decreasing when the diameter is 10 cm?
Volume of a sphere in terms of diameter:
Rate of volume:
Rate of diameter:
I'm not sure what to do at this point
Just in case a picture helps...
... where (key in spoiler) ...
Spoiler:
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Don't integrate - balloontegrate!
Balloon Calculus; standard integrals, derivatives and methods
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Don't you see that we can cancel dD? (Half kidding.) Seriously, this is the chain rule.
By seeing that you are trying to differentiate a composite function of t with respect to t. And the chain rule says this will involve differentiating with respect to the whole of the inner function of t. (D is the inner function of t.)
is the chain rule. Check your Calculus text.
The problem asks you to find and you are told . " ", which you can easily get from the formula for V in terms of D, is the "missing link" in the chain rule.
We choose to represent the function V(t) as V(D(t)). The chain rule says that .
Properly speaking, where something came from is not a mathematical question. The solution to this question is a sequence of statements, each of which is either true or false (hopefully, true). The only proper question is why a certain statement is true.
Edit: Yes, it's legitimate to ask metamathematical questions, such as what reasoning one used to come up with a certain solution. Hopefully, post #8 answered this question.
It makes more sense to use the Chain rule now that I see there is a function V(D(t)). I did not know this was the function that I was supposed to use to solve the problem. The issue I am having is how to formulate the problem so I can solve it. I did not know to express the volume as the diameter when the time changes the diameter...I am still a bit confused as to how I can get this, but I think I will skip this one for now and come back to it later because I have other problems I need to finish as well as other classes.
Oh, I see now. Taking the derivative of the Volume with respect to time:
However, taking the derivative of the diameter results in using the Chain rule which I get.
I just didn't know how to come up with the formula: to solve this. All I needed was to know how to arrive at which I didn't know how to in the first place.
There is never a function that your are supposed to use to solve a problem- look at all functions and formulas that have anything to do with the problem.
In this case you are told that "a snowball melts in volume @ 1 cc/min" so the rate of change of V with respect to t is surely relevant.
The issue I am having is how to formulate the problem so I can solve it. I did not know to express the volume as the diameter when the time changes the diameter...I am still a bit confused as to how I can get this, but I think I will skip this one for now and come back to it later because I have other problems I need to finish as well as other classes.