Chapter 1, Equations and Graphs - Section 1.10 - Modeling Variation - 1.10 Exercises - Page 164: 25

$W= \frac{360}{r^{2}}$

Since $W$ is inversely proportional to the square of $r$, we have: $W= \frac{k}{r^{2}}$ We are given: $W=10$ and $r=6$, so we have: $10= \frac{k}{6^{2}}$ $k=36*10=360$ So the equation is: $W= \frac{360}{r^{2}}$