To be more precise, sound film runs (with some oddball exceptions) at 24 frames per second or 90 feet a minute, so a film that runs 7,647 feet would be 85 minutes (84.96 minutes to be precise).
Running times for silent films are tricker because speeds varied trough the years. The standards arrived at in the mid to late 1920s were to photograph at 20 frames per second and to project at 24 frames per second, but in the teens it was common to project at 16 fps, gradually moving up to 20-22 fps in the early 1920s.