SOLUTION: if y varies inversely as the cube of x, and y=64 when x=3,Find the value of x when y=216.

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Question 414298: if y varies inversely as the cube of x, and y=64 when x=3,Find the value of x when y=216.
Found 2 solutions by josmiceli, ewatrrr:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Note: k is called the constant of proportionality
y+=+k%2A%281%2Fx%5E3%29
64+=+k%2A%281%2F3%5E3%29
64+=+k%2A%281%2F27%29
k+=+27%2A64
k+=+1728
-----------
216+=+1728%2A%281%2Fx%5E3%29
x%5E3+=+1728%2F216
x%5E3+=+8
x+=+root%283%2C8%29
x+=+2

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

y varies inversely as the cube  of x  OR y = k/x^3

 y=64 when x=3  64 = k/27  k = 1728

Find the value of x when y = 216. 

 216 = 1728/x^3

+x%5E3+=+%281728%29%2F216

   x^3  = 8

    x = 2