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## A spherical balloon is inflated with helium at a rate of 140pift^3/min How fast is the balloon’s radius increasing when the radius is 7ft

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## Answers ( )

Answer:

dr = 0.71 ft/min

the balloon’s radius is increasing at 0.71 ft/min when the radius is 7ft.

Explanation:

Given;

Rate of inflation dV = 140pift^3/min

Radius r = 7 ft

Change in radius = dr

Volume of a spherical balloon is;

V = (4/3)πr^3

The change in volume can be derived by differentiating both sides;

dV = (4πr^2)dr

Making dr the subject of formula;

dr = dV/(4πr^2)

Substituting the given values;

dr = 140π/(4π×7^2)

dr = 0.714285714285 ft/min

dr = 0.71 ft/min

the balloon’s radius is increasing at 0.71 ft/min when the radius is 7ft.