The radius of a cone is decreasing at a constant rate of 8 feet per minute. The volume remains a constant 54 cubic feet. At the instant when the height of the cone is 66 feet, what is the rate of change of the height? The volume of a cone can be found with the equation V=13πr2h.V=31​πr2h. Round your answer to three decimal places.

Algebra for College Students
10th Edition
ISBN:9781285195780
Author:Jerome E. Kaufmann, Karen L. Schwitters
Publisher:Jerome E. Kaufmann, Karen L. Schwitters
Chapter10: Exponential And Logarithmic Functions
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The radius of a cone is decreasing at a constant rate of 8 feet per minute. The volume remains a constant 54 cubic feet. At the instant when the height of the cone is 66 feet, what is the rate of change of the height? The volume of a cone can be found with the equation V=13πr2h.V=31​πr2h. Round your answer to three decimal places.

Expert Solution
Step 1

Let the radius of cone is r feet and it’s height

Be h feet.

Then given that its radius is decreasing at a constant rate 8 feet/minute

And its volume  V = 54 feet3

Then at h= 66 feet, we have to find dh/dt

Since volume af cone v = 1/3πr2h

When r = 54, h = 66 then

54 = π/3r2(66)

  • Πr2/3 = 54/66
  • r2 = 54/66 x 3/π = 0.78
  • r =0.884 feet
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