If the radius of a sphere is \(r\) and its volume is \(v\), then
\(v=\cfrac{4}{3}\pi r^3\)
\(\because \cfrac{4}{3}\pi\) is a constant value
\(\therefore v\propto r^3\)
If the radius of a sphere is \(r\) and its volume is \(v\), then \(v \propto r^3\).