[tex]16. \ \ V= \pi r^2h \ \to \ r^2= \cfrac{V}{ \pi h} \ \to \ \boxed{r= \sqrt{ \frac{V}{ \pi h} } } \\ \\ \\ 17.\ \ d= \frac{1}{2} at^2 \ \to \ 2d= at^2 \ \to \ t^2= \cfrac{2d}{a} \ \to \ \boxed{t= \sqrt{\frac{2d}{a}}} \\ \\ \\ 18. \ \ S=180(n-2) \ \to \ \cfrac{S}{180}=n-2 \ \to \ \boxed{n= \frac{S}{180}+2 } [/tex]
