SOLUTION: A large snowball with a radius of 2.1 feet is melting so the radius is decreasing at 0.4 feet per hour. How fast is the surface area changing when when the radius is 0.8 feet?

Question 1111440: A large snowball with a radius of 2.1 feet is melting so the radius is decreasing at 0.4 feet per hour. How fast is the surface area changing when when the radius is 0.8 feet?
Round your answer to 2 decimal places.
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A large snowball with a radius of 2.1 feet is melting so the radius is decreasing at 0.4 feet per hour. How fast is the surface area changing when the radius is 0.8 feet?
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SA = 4pi*r^2
dSA/dt = 4pi*2r*dr/dt
dSA/dt = 4pi*2*0.8*0.4 sq ft/hr
= 2.56pi sq ft/hr

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