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I am 99% positive I did a) correctly, as the answer is correct according to the answer in the back of my text book. However, I cannot do b).

The question: A spherical balloon is being inflated. Find the rate of change of the surface area with respect to the radius when:

a) The radius is 5cm

b) The surface area is 200cm^{2}

The attempt at a solution

a) 8[itex]\pi[/itex]*5cm

=125.66 cm^{2}/cm (or 40[itex]\pi[/itex] cm^{2}/cm)

b) I am unsure of what to do for this. Is it something like:

[itex]\sqrt{}200/4\pi[/itex]

=3.9894

And then do something else, which I don't know what that is.

The answer to this question, according to the book, is 100.27cm^{2}/cm

Sorry if the equations don't look very clear. This is my first post and I will learn how to write it all up neatly when I am not so tired.

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# Homework Help: Rate of change (surface area/radius)

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