SOLUTION: The surface area of a sphere varies directly as the square of a radius. a. if the surface area is 16pi when r is 2, find the constant of variation. b. Find the surface area whe

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: The surface area of a sphere varies directly as the square of a radius. a. if the surface area is 16pi when r is 2, find the constant of variation. b. Find the surface area whe      Log On


   

Question 413927: The surface area of a sphere varies directly as the square of a radius.
a. if the surface area is 16pi when r is 2, find the constant of variation.
b. Find the surface area when the radius is 5.
c. Find the radius when the surface area is 48 pi.
Answer by ewatrrr(24785) About Me  (Show Source):
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Hi

The surface area of a sphere varies directly as the square of a radius.

a. if the surface area is 16pi  when r  is 2, find the constant of variation.

   16pi = k*4

    4pi = k



b. Find the surface area when the radius is 5. S%5BA%5D+=+4pi%2A25+=+100pi



c. Find the radius when the surface area is 48 pi:   kr^2 = 48pi

  r^2 = 48pi/4pi = 12   r = sqrt(12)  or r = 2sqrt(3)