Find the fourth proportional of the numbers $20$, $32$ and $36$.

Let the fourth proportional to $a$, $b$, and $c$ be $x$.The relationship is given by:
$$\frac{a}{b}=\frac{c}{x}$$
Given $a=20$, $b=32$, and $c=36$:
$$\frac{20}{32}=\frac{36}{x}$$
Simplifying the fraction on the left side:
$$\frac{5}{8}=\frac{36}{x}$$
Cross-multiplying to solve for $x$:
$$5x=36\times 8$$
$$5x=288$$
$$x=\frac{288}{5}=57.6$$
Thus, the fourth proportional is $57.6$.