To convert from feet per minute to feet per second we first need to know how much is 1 minute in seconds
[tex]\begin{gathered} 1\min \to60\sec \\ \frac{1\min }{60\sec }\to\text{change factor} \end{gathered}[/tex]Now we multiply the change factor by the value we want to convert:
[tex]\begin{gathered} 1200\frac{ft}{\min}\cdot\frac{1\min }{60\sec } \\ \frac{1200}{60}\frac{ft}{\sec}\to20\frac{ft}{\sec } \\ \end{gathered}[/tex]