A model plane flies 18ft per 2 seconds. What is the plane's speed in miles per hour? Round to the nearest tenths.
18 ft / 2 seconds
= 9 ft/sec
= (9/5280) miles / (1/3600) hours
= (9/5280)(3600/1) m/h
= (135/22) mph
= appr 6.1 mph
or
18 ft in 2 seconds
= 9 ft in 1 second
= 540 ft in 1 minute
= 32400 ft in 1 hour
= 6.1 mph