Boomerang 15.3 ft/s
Greased Lightning 25.74 ft/s
space mountain 26.25 ft/s
Rajun Cajun 15.3 ft/s
flight of Icarus 15.3 ft/s
To calculate the rate, the formula is s= d/t where s = speed, d= distance in feet, t= time in seconds. The roller coasters that has a proportional relationship are boomerang, rajun cajun, and flight of Icarus as they all have the same rate.
