Growing Balloon
Algebra
Level
pending
A spherical balloon has an original radius of 3cm that increases at a rate of 0.1 cm/sec, after starting to pump in air. The rate of change of the surface area at time 10 seconds is . Find k.
The answer is 3.2.
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1 solution
dA/dt=dr/dt* dA/dr where dr/dt=0.1 cm/s and dA/dr= 8 pi r after 10 seconds, r= 4. Therefore, dA/dt= 0.1 8 pi*4= 3.2