Answer
$81:1$
Work Step by Step
The given values are
Radius of the large piston $r_l=18\;in.$
Radius of the small piston $r_s=2\;in.$
Formula for the mechanical advantage is
$\Rightarrow MA=\frac{r^2_l}{r^2_s}$
Substitute all the values.
$\Rightarrow MA=\frac{18^2}{2^2}$
Cross multiply.
$\Rightarrow MA=\frac{81}{1}$
Hence, the $MA$ is $81:1$.
