Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.1 Inverse Functions - 4.1 Exercises - Page 418: 90

The radius $r\ (in)$ for a sphere with volume $V=5\ in^3$

If $f(r)$ is the volume of a sphere of radius $r$, then $f^{-1}(V)$ will represent the radius with volume $V$. Thus $f^{-1}(5)$ represents the radius $r\ (in)$ for a sphere with volume $V=5\ in^3$