We are already given the magnitude of the speed which is 1,100 ft/s. All we have to do is convert this to miles per hour. So, we have to know the conversion factor. Note that there are 5,280 ft in 1 mile, and 3,600 s in 1 hr. The solution is as follows:
(1,100 ft/s)(1 mile/5,280 ft)(3,600 s/1 h) = 750 mph
