Question 413927
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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[A] = 4pi*25 = 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)