Dear Christina:
Good for you for flogging those units conversions problems!
You can tell your students they are not hard:
16 knots = 16 nautical miles per hour = (16 x 2000) yards per hour = 32,000 yards per hour = 96,000 feet per hour (three feet in every yard) = 18.2 miles per hour (divide by 5280 feet per mile.) But round it to just 18 mph.
your fan, Michael Wing