If M varies inversely as the cube of r, and M = 8 when R = 4

Question

A) Find the constant of variation

B) Find M when r = 5

Answer 1

M = k/r^3

8 = k/4^3

8 * 4^3 = k

k=512

M = 512/5^3 = 512/125 = 4.096