1 foot= 12 inches.
To convert you must have "2 fractions" to multiply.
Your first fraction must be 100in/1min. (100 inches per 1 minute).
The second should serve to convert inches to feet. It should be 1 foot/ 12 inches. (1 foot per 12 inches).
Your product should be 100ft/12 which equals 8.3 repeating or 25/3 (8 1/3) feet.