Which speed is the fastest?
18 ft. in 20 minutes
90ft. in 2.5 hours
20 yards in 1.5 hour
32/3 yards in 15 minutes

Fastest: 32/3 yards in 15 minutes

18 ft/20 min = .9 ft/min
90 ft/2.5 hrs = 90 ft/150 min = .6 ft/min
20 yd/1.5 hr = 60 ft/90 min = .667 ft/min 
32/3 yd/15 min = 32 ft/15 min = 2.133 ft/min