Answer
$\frac{ds}{dt}=1\frac{cm}{min}$
Work Step by Step
Given
$s=20$
$\frac{dV}{dt}=1200$
$V=s^3$
on differentiating above, we get:
$\frac{dV}{dt}=3s^2\frac{ds}{dt}$
$\frac{dV}{dt}=3\times20^2\frac{ds}{dt}$
$\frac{ds}{dt}=\frac{1200}{1200}=1$
thus,
$\frac{ds}{dt}=1\frac{cm}{min}$
