Posted by **Vince** on Sunday, March 15, 2009 at 10:03pm.

Air is being pumped into a spherical balloon so that its volume increases at a rate of 90{cm}^3/s. How fast is the surface area of the balloon increasing when its radius is 7{cm}? Recall that a ball of radius r has volume \displaystyle V={4}/{3}pie r^3 and surface area S=4\pi r^2

- Calc -
**bobpursley**, Sunday, March 15, 2009 at 10:20pm
dV/dt= 4/3 PI 3 r^2 dr/dt

solve for dr/dt given dv/dt

Then dS/dt=4PI 2r dr/dt, knowing dr/dt solve for dS/dt

and it is done.

- Calc -
**Vince**, Sunday, March 15, 2009 at 10:26pm
ok thanks alot for clearing it up

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